Interlayer video encoding method and apparatus and interlayer video decoding method and apparatus for compensating luminance difference

ABSTRACT

An interlayer video decoding method comprises reconstructing a first layer image based on encoding information acquired from a first layer bitstream; reconstructing a second layer current block determined as a predetermined partition mode and a prediction mode by using interlayer prediction information acquired from a second layer bitstream and a first layer reference block corresponding to a current block of a first layer reconstruction image that is to be reconstructed in a second layer; determining whether to perform luminance compensation on the second layer current block in a partition mode in which the second layer current block is not split; and compensating for luminance of the second layer current block according to whether luminance compensation is performed and reconstructing a second layer image including the second layer current block of which luminance is compensated for.

TECHNICAL FIELD

The present invention relates to interlayer video encoding and decodingmethods, and more particularly, to a method of compensating for aluminance difference between interlayer images.

BACKGROUND ART

As hardware for reproducing and storing high resolution or high qualityvideo content is being developed and supplied, a need for a video codecfor effectively encoding or decoding the high resolution or high qualityvideo content is increasing. According to a conventional video codec, avideo is encoded according to a limited encoding method based on acoding unit having a predetermined size.

Image data of the space domain is transformed into coefficients of thefrequency domain via frequency transformation. According to a videocodec, an image is split into blocks having a predetermined size,discrete cosine transformation (DCT) is performed on each block, andfrequency coefficients are encoded in block units, for rapid calculationof frequency transformation. Compared with image data of the spacedomain, coefficients of the frequency domain are easily compressed. Inparticular, since an image pixel value of the space domain is expressedaccording to a prediction error via inter prediction or intra predictionof a video codec, when frequency transformation is performed on theprediction error, a large amount of data may be transformed to 0.According to a video codec, an amount of data may be reduced byreplacing data that is consecutively and repeatedly generated withsmall-sized data.

A multi-layer video codec encodes and decodes a first layer video andvarious second layer videos to remove temporal and spatial redundanciesof the first layer video and the second layer videos and redundancybetween layers, thereby reducing an amount of data of the first layervideo and the second layer videos.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

If luminance is not identical between videos for each view, since theamount of interlayer prediction errors further increases, encodingefficiency may be reduced. Accordingly, considering luminanceinconsistency between views, a luminance compensation determiner 14 ofan interlayer video encoding apparatus 10 may compensate for and encodea luminance difference of video for each view. For example, a luminancedifference between a first view image encoded by a first layer encoder12 and a second view image encoded by a second layer encoder 16 may beencoded. Since the luminance difference of the second view image withrespect to the first view image is encoded, luminance may be compensatedfor when the second layer encoder 16 encodes a second view video.However, complexity may increase in order to enable compensation for theluminance.

Technical Solution

According to an embodiment of the present invention, an interlayer videodecoding method comprises reconstructing a first layer image based onencoding information acquired from a first layer bitstream;reconstructing a second layer current block determined as apredetermined partition mode and a prediction mode by using interlayerprediction information acquired from a second layer bitstream and afirst layer reference block corresponding to a current block of a firstlayer reconstruction image that is to be reconstructed in a secondlayer; determining whether to perform luminance compensation on thesecond layer current block in a partition mode in which the second layercurrent block is not split; and compensating for luminance of the secondlayer current block according to whether luminance compensation isperformed and reconstructing a second layer image including the secondlayer current block of which luminance is compensated for.

Advantageous Effects of the Invention

According to an embodiment of the present invention, a luminancecompensation application range of a multilayer image is appropriatelyrestricted, thereby maintaining encoding efficiency and reducingcomplexity.

DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1A is a block diagram of an interlayer video encoding apparatus,according to various embodiments;

FIG. 1B is a flowchart of an interlayer video encoding method, accordingto various embodiments;

FIG. 2A is a block diagram of an interlayer video decoding apparatus,according to various embodiments;

FIG. 2B is a flowchart of an interlayer video decoding method, accordingto various embodiments;

FIG. 3 illustrates an inter-layer prediction structure, according to anembodiment;

FIG. 4 is a flowchart of a method in which an interlayer video decodingapparatus performs luminance compensation, according to an embodiment;

FIG. 5 illustrates an example of syntax for performing luminancecompensation based on a partition mode of a current block, according toan embodiment;

FIG. 6 illustrates another example of syntax for performing luminancecompensation based on a partition mode of a current block, according toan embodiment;

FIG. 7 is a block diagram of a video encoding apparatus based on codingunits according to a tree structure, according to an embodiment;

FIG. 8 is a block diagram of a video decoding apparatus based on codingunits according to a tree structure, according to an embodiment;

FIG. 9 is a diagram for describing a concept of coding units accordingto an embodiment;

FIG. 10 is a block diagram of an image encoder based on coding units,according to an embodiment;

FIG. 11 is a block diagram of an image decoder based on coding units,according to an embodiment;

FIG. 12 is a diagram illustrating deeper coding units and partitions,according to an embodiment;

FIG. 13 is a diagram for describing a relationship between a coding unitand transformation units, according to an embodiment;

FIG. 14 is a diagram for describing encoding information of codingunits, according to an embodiment;

FIG. 15 is a diagram of deeper coding units, according to an embodiment;

FIGS. 16 through 18 are diagrams for describing a relationship betweencoding units, prediction units, and transformation units, according toan embodiment;

FIG. 19 is a diagram for describing a relationship between a codingunit, a prediction unit, and a transformation unit, according toencoding mode information of Table 1;

FIG. 20 is a diagram of a physical structure of a disc in which aprogram is stored, according to an embodiment;

FIG. 21 is a diagram of a disc drive for recording and reading a programby using a disc;

FIG. 22 is a diagram of an overall structure of a content supply systemfor providing a content distribution service;

FIGS. 23 and 24 are diagrams respectively of an external structure andan internal structure of a mobile phone to which a video encoding methodand a video decoding method are applied, according to an embodiment;

FIG. 25 is a diagram of a digital broadcast system to which acommunication system is applied, according to an embodiment; and

FIG. 26 is a diagram illustrating a network structure of a cloudcomputing system using a video encoding apparatus and a video decodingapparatus, according to an embodiment.

BEST MODE

According to an aspect of an embodiment of the present invention, aninterlayer video decoding method comprises reconstructing a first layerimage based on encoding information acquired from a first layerbitstream; reconstructing a second layer current block determined as apredetermined partition mode and a prediction mode by using interlayerprediction information acquired from a second layer bitstream and afirst layer reference block corresponding to a current block of a firstlayer reconstruction image that is to be reconstructed in a secondlayer; determining whether to perform luminance compensation on thesecond layer current block in a partition mode in which the second layercurrent block is not split; and compensating for luminance of the secondlayer current block according to whether luminance compensation isperformed and reconstructing a second layer image including the secondlayer current block of which luminance is compensated for.

When the second layer current block has a size of 2N×2N, the partitionmode in which the second layer current block is not split is a 2N×2Npartition mode.

The determining of whether to perform luminance compensation comprises:acquiring partition mode information and prediction mode information ofa second layer block from the second layer bitstream; when the partitionmode information is the partition mode in which the second layer currentblock is not split and the prediction mode information is not an intraprediction mode, acquiring luminance compensation information for thesecond layer block from the second layer bitstream; and determiningwhether to perform luminance compensation on the second layer currentblock based on the luminance compensation information for the secondlayer block.

The determining of whether to perform luminance compensation comprises:when the prediction mode information is not an intra prediction mode,acquiring luminance compensation information from the second layerbitstream.

The determining of whether to perform luminance compensation comprises:acquiring the luminance compensation information for a current blockincluded in a slice determined to use luminance compensation based onthe prediction mode information.

An operation of determining whether to perform luminance compensation onsecond layer blocks except for blocks decoded as the partition mode inwhich the second layer current block is not split is omitted, andluminance compensation is not performed on the second layer blocks.

The determined prediction mode is a merge mode or an advanced motionvector prediction (AMVP) mode.

According to an aspect of an embodiment of the present invention, aninterlayer video encoding method comprises generating a first layerbitstream including encoding information generated by encoding a firstlayer image; reconstructing a second layer current block by using afirst layer reference block corresponding to a second layer currentblock that is to be reconstructed in a first layer reconstruction imageaccording to a predetermined partition mode and a prediction mode;determining whether to perform luminance compensation on the secondlayer current block in a partition mode in which the second layercurrent block is not split; and generating a second layer bitstreamincluding interlayer prediction information between the second layercurrent block of which luminance is determined according to whetherluminance compensation is performed and the first layer reference block.

When the second layer current block has a size of 2N×2N, the partitionmode in which the second layer current block is not split is a 2N×2Npartition mode.

The determining of whether to perform luminance compensation comprises:determining partition mode information and prediction mode informationof a second layer block; when the partition mode information is thepartition mode in which the second layer current block is not split andthe prediction mode information is not an intra prediction mode,determining luminance compensation information indicating whether toperform luminance compensation on the second layer block; and thegenerating of the second layer bitstream comprises: generating thesecond layer bitstream including the partition mode information, theprediction mode information, and the luminance compensation information.

The determining of whether to perform luminance compensation comprises:when the prediction mode information is not an intra prediction mode,determining the luminance compensation information indicating whether toperform luminance compensation on the second layer block.

The determining of whether to perform luminance compensation comprises:determining the luminance compensation information for a current blockincluded in a slice determined to use luminance compensation based onthe prediction mode information.

An operation of determining whether to perform luminance compensation onsecond layer blocks except for blocks decoded as the partition mode inwhich the second layer current block is not split is omitted, andluminance compensation is not performed on the second layer blocks.

The determined prediction mode is a merge mode or an advanced motionvector prediction (AMVP) mode.

According to an aspect of an embodiment of the present invention, aninterlayer video decoding apparatus comprises a first layer decoder forreconstructing a first layer image based on encoding informationacquired from a first layer bitstream; a second layer decoder forreconstructing a second layer current block determined as apredetermined partition mode and a prediction mode by using interlayerprediction information acquired from a second layer bitstream and usinga first layer reference block corresponding to a current block of afirst layer reconstruction image that is to be reconstructed in a secondlayer; and a luminance compensation determiner for determining whetherto perform luminance compensation on the second layer current block in apartition mode in which the second layer current block is not split,wherein the second layer decoder compensates for luminance of the secondlayer current block according to whether luminance compensation isperformed and reconstructs a second layer image including the secondlayer current block of which luminance is compensated for.

According to an aspect of an embodiment of the present invention, aninterlayer video encoding apparatus comprises a first layer encoder forgenerating a first layer bitstream including encoding informationgenerated by encoding a first layer image; a second layer encoder forreconstructing a second layer current block by using a first layerreference block corresponding to a second layer current block that is tobe reconstructed in a first layer reconstruction image according to apredetermined partition mode and a prediction mode; and a luminancecompensation determiner for determining whether to perform luminancecompensation on the second layer current block in a partition mode inwhich the second layer current block is not split, wherein the secondlayer encoder generates a second layer bitstream including interlayerprediction information between the second layer current block of whichluminance is determined according to whether luminance compensation isperformed and the first layer reference block.

According to another aspect of an embodiment of the present invention,there is provided a non-transitory computer-readable recording mediumhaving recorded thereon a computer program for executing the method.

MODE OF THE INVENTION

Hereinafter, an interlayer video encoding method and an interlayer videodecoding method of determining whether to perform luminance compensationbased on block characteristics according to various embodiments will bedescribed with reference to FIGS. 1A through 6. A video encoding methodand a video decoding method, based on coding units having a treestructure according to various embodiments that are applicable to theinterlayer video encoding method and the interlayer video decodingmethod will be described with reference to FIGS. 7 through 19. Inaddition, various embodiments to which the video encoding method and thevideo decoding method will be described with reference to FIGS. 20through 26.

Hereinafter, an ‘image’ may denote a still image or a moving image of avideo, or a video itself.

Hereinafter, a ‘sample’ that is data allocated to a sampling location ofan image may mean data that is a processing target. For example, pixelsin an image of a spatial area may be samples.

An interlayer video encoding apparatus and method and an interlayervideo decoding apparatus and method according to an embodiment will nowbe described with reference to FIGS. 1A through 7.

FIG. 1A is a block diagram of an interlayer video encoding apparatus 10,according to various embodiments. FIG. 1B is a flowchart of aninterlayer video encoding method, according to various embodiments.

The interlayer video encoding apparatus 10 according to variousembodiments may include a first layer encoder 12, a luminancecompensation determiner 14, and a second layer encoder 16. The luminancecompensation determiner 14 may be included in the second layer encoder16. The luminance compensation determiner 14 may be located outside thesecond layer encoder 16.

The interlayer video encoding apparatus 10 according to variousembodiments may classify and encode a plurality of image sequences foreach layer according to scalable video coding and may output a separatestream including data encoded for each layer. The interlayer videoencoding apparatus 10 may encode first layer image sequences and secondlayer image sequences according to different layers.

The first layer encoder 12 may encode first layer images and output afirst layer stream including encoding data of the first layer images.

The second layer encoder 16 may encode second layer images and output asecond layer stream including encoding data of the second layer images.

For example, according to scalable video coding based on spatialscalability, low resolution images may be encoded as the first layerimages, and high resolution images may be encoded as the second layerimages. An encoding result of the first layer images may be output in afirst layer stream. An encoding result of the second layer images may beoutput in a second layer stream.

As another example, a multi-view video may be encoded according toscalable video coding. In this case, center view images may be encodedas first layer images, and left view images and right view images may beencoded as second layer images that refer to the first layer images.Alternatively, when the interlayer video encoding apparatus 10 permitsthree or more layers such as first, second, and third layers, the centerview images may be encoded as the first layer images, the left viewimages may be encoded as the second layer images, and the right viewimages may be encoded as third layer images. However, the presentinvention is not necessarily limited thereto. Layers that the centerview images, the left view images, and the right view images are encodedand referred may be changed.

As another example, scalable video coding may be performed according totemporal hierarchical prediction based on temporal scalability. A firstlayer stream including encoding information generated by encoding imagesof a base frame rate may be output. Temporal levels may be classifiedfor each frame rate and may be respectively encoded in layers. A secondlayer stream including encoding information of a high speed frame ratemay be output by further encoding images of the high frame rate withreference to the images of the basic frame rate.

Scalable video coding may be performed on a first layer and a pluralityof second layers. In the presence of three or more second layers, firstlayer images, first second layer images, second second layers images, .. . , Kth second layer images may be encoded. Accordingly, an encodingresult of the first layer images may be output in the first layerstream, and encoding results of the first second layer images, secondsecond layers images, . . . , Kth second layer images may berespectively output in first, second, . . . Kth second layer streams.

The interlayer video encoding apparatus 10 according to variousembodiments may perform inter prediction for predicting a current imageby referring to images of a single layer. A motion vector indicatingmotion information between the current image and a reference image and aresidual between the current image and the reference image may begenerated through inter prediction.

The interlayer video encoding apparatus 10 may perform inter-layerprediction for predicting prediction information of second layer imagesby referring to prediction information of the first layer images.

When the interlayer video encoding apparatus 10 according to anembodiment permits three or more layers such as a first layer, a secondlayer, a third layer, etc., the interlayer video encoding apparatus 10may perform inter-layer prediction between a first layer image and athird layer image and inter-layer prediction between a second layerimage and the third layer image according to a multi-layer predictionstructure.

A position differential component between the current image and areference image of a different layer and a residual between the currentimage and the reference image of the different layer may be generatedthrough inter-layer prediction.

An inter-layer prediction structure will be described in detail withreference to FIG. 3 later.

The interlayer video encoding apparatus 10 according to variousembodiments encodes each video image for each respective block accordingto each layer. A block may have a square shape, a rectangular shape, orany geometric shape and is not limited to a data unit having apredetermined size. A block may be a maximum coding unit, a coding unit,a prediction unit, a transformation unit, or the like from among codingunits according to a tree structure. The maximum encoding unit includingcoding units having the tree structure is diversely referred to as acoding block unit, a block tree, a root block tree, a coding tree, acoding root or a tree trunk. Video encoding and decoding methods basedon coding units having the tree structure will now be described withreference to FIGS. 8 through 20.

Inter prediction and inter layer prediction may be performed based on adata unit of the coding unit, the prediction unit, or the transformationunit.

The first layer encoder 12 according to various exemplary embodimentsmay perform source coding operations including inter prediction or intraprediction on the first layer images to generate symbol data. The symboldata represents a sample value of each coding parameter and a samplevalue of the residual.

For example, the first layer encoder 12 may perform inter prediction, orintra prediction, transformation and quantization on samples in a dataunit of the first layer images, generate symbol data, perform entropyencoding on the symbol data, and generate a first layer stream.

The second layer encoder 16 may encode the second layer images based onthe coding units having the tree structure. The second layer encoder 16may perform inter/intra prediction, transformation and quantization onsamples in a data unit of the second layer images, generate symbol data,perform entropy encoding on the symbol data, and generate an secondlayer stream.

The second layer encoder 16 according to various embodiments may performinter layer prediction that predicts a second layer image by usingprediction information of a first layer image. The second layer encoder16 may determine prediction information of a second layer current imageby using prediction information of a first layer reconstructed image andgenerate a second layer prediction image based on the determinedprediction information to encode a prediction error between a secondlayer original image and the second layer prediction image, in order toencode the second layer original image among the second layer imagesequences through the inter layer prediction structure.

The second layer encoder 16 may perform inter layer prediction on thesecond layer image for each block such as the coding unit or theprediction unit and determine a block of the first layer image to whicha block of the second layer image is to refer. For example, areconstruction block of the first layer image positioned incorrespondence to a position of a current block image in the secondlayer image may be determined. The second layer encoder 16 may determinea second layer prediction block by using the first layer reconstructionblock corresponding to the second layer block.

The second layer encoder 16 may use the second layer prediction blockdetermined by using the first layer reconstruction block as a referenceimage for inter layer prediction of a second layer original block. Thesecond layer encoder 16 may perform entropy encoding on an error betweena sample value of the second layer prediction block and a sample valueof the second layer original block, i.e., a residual according to interlayer prediction, using the first layer reconstruction image.

As described above, the interlayer video encoding apparatus 10 mayencode a current layer image sequence by referring to first layerreconstruction images through the inter layer prediction structure.However, the interlayer video encoding apparatus 10 according to variousembodiments may encode the second layer image sequence according to asingle layer prediction structure without referring to different layersamples. Thus, it is not limited to construe that the second layerencoder 16 performs only inter-layer prediction in order to encode thesecond layer image sequence.

As described above, when the interlayer video encoding apparatus 10encodes a multi-view video, the first layer encoder 12 may encode afirst view video, and the second layer encoder 16 may encode a secondview video. Video for each view may be captured by different cameras ormay be acquired using different lenses. Since characteristics of acapturing angle, illumination, or an imaging tool (a camera, a lens,etc.) for each view may be different, a phenomenon may occur wherebyluminance is not identical between videos acquired for each view. Such aluminance mismatch phenomenon may be related to a difference in a samplevalue between videos for each view.

If luminance is not identical between videos for each view, since theamount of interlayer prediction errors further increases, encodingefficiency may be reduced. Accordingly, considering luminanceinconsistency between views, the luminance compensation determiner 14 ofthe interlayer video encoding apparatus 10 may compensate for and encodea luminance difference of video for each view. For example, a luminancedifference between a first view image encoded by the first layer encoder12 and a second view image encoded by the second layer encoder 16 may beencoded. Since the luminance difference of the second view image withrespect to the first view image is encoded, luminance may be compensatedfor when the second layer encoder 16 encodes a second view video.

A predetermined parameter may be used to compensate for a luminancedifference between a first layer block and a second layer blockaccording to an embodiment. For example, as shown in Equation 1 below, ascale factor a and an offset value b may be used to acquire a result P′by compensating for luminance with respect to a pixel P of a currentblock corresponding to a different layer.P′=aXP+b  [Equation 1]

The parameter for compensating for the luminance difference in a blockunit may be transmitted by being included in a bitstream or may beinduced by utilizing peripheral pixel values of a second layer currentblock and peripheral pixel values of a first layer reconstruction blockcorresponding to the current block.

Meanwhile, since residuals are predicted between layers in an interlayer prediction structure, an encoding operation of predicting aluminance difference between layers may increase an amount of arithmeticoperations. Accordingly, the luminance compensation determiner 14according to various embodiments may determine whether to performluminance compensation in consideration of characteristics in apredetermined data unit such as a slice of a current image or a block.

A detailed operation of the interlayer video encoding apparatus 10 thatconsiders compensation of luminance will be described with reference toFIG. 1B below.

FIG. 1B is a flowchart of an interlayer video encoding method, accordingto various embodiments.

In operation 11, the first layer encoder 12 may encode a first layerimage and generate a first layer bitstream including sample values ofgenerated encoding information.

In operation 13, the second layer encoder 16 may encode a second layerimage and reconstruct a second layer current block that is determined asa predetermined partition mode and prediction mode, in order to generatea second layer bitstream including sample values of generated encodinginformation. That is, the second layer encoder 16 may reconstruct thesecond layer current block using a first layer reference blockcorresponding to the second layer current block that is to bereconstructed in a first layer reconstruction image according to thepredetermined partition mode and prediction mode. It may be interpretedthat if the interlayer video encoding apparatus 10 encodes a multiviewvideo, the first layer image corresponds to a first view image, and thesecond layer image corresponds to a second view image. The first layerencoder 12 and the second layer encoder 16 may split each image intoblocks and encode each image for each respective block.

In operation 15, the luminance compensation determiner 14 may determinewhether to perform luminance compensation on the second layer currentblock in the partition mode in which the second layer current block isnot split. In this regard, the partition mode in which the second layercurrent block is not split may mean that a partition mode of a currentblock is a 2N×2N partition mode when a size of the current block is2N×2N.

In operation 17, the second layer encoder 16 may generate a second layerbitstream including inter layer prediction information between thesecond layer current block of which luminance is determined according towhether to perform luminance compensation and the first layer referenceblock.

For example, the second layer encoder 16 may generate the second layerbitstream including partition mode information, prediction modeinformation, and luminance compensation information for a second layerreconstruction block of the partition mode in which the second layercurrent block is not split and of a prediction mode other than an intraprediction mode. The second layer encoder 16 may perform inter layerprediction that encodes an error between the first layer image and thesecond layer image, and thus residuals between blocks (second layerblocks) of the second layer image and reference blocks (first layerreference blocks) of the first layer image corresponding to the blocksof the second layer image may be encoded. Thus, the second layerbitstream may include various pieces of inter layer predictioninformation indicating inter layer encoding methods and inter layerresiduals.

Operations 13 and 15 will now be described in more detail.

The second layer encoder 16 may determine partition mode informationindicating a partition mode of a second layer block and prediction modeinformation indicating a prediction mode of the second layer block. Forexample, the partition mode information of the second layer block may bedetermined in a merge mode or advanced motion vector prediction (AMVP)mode. The second layer encoder 16 may reconstruct the second layercurrent block by using the first layer reference block corresponding tothe second layer current block that is to be reconstructed in the firstlayer reconstruction image according to the predetermined partition modeand prediction mode.

The luminance compensation determiner 14 may determine whether toperform luminance compensation on the second layer block determinedusing the first layer reference block corresponding to the second layerblock in the first layer reconstruction image. That is, the luminancecompensation determiner 14 may determine whether to perform luminancecompensation on the second layer block determined as the predeterminedpartition mode and prediction mode. For example, the luminancecompensation determiner 14 may determine luminance compensationinformation indicating whether to perform luminance compensation on thesecond layer block when the partition mode information of the secondlayer block is the partition mode in which the second layer currentblock is not split and the prediction mode is not an intra predictionmode.

For example, the luminance compensation determiner 14 may determineluminance compensation information for a block indicating that thepartition mode information is a 2N×2N partition mode.

For example, the luminance compensation determiner 14 may determineluminance compensation information for a block indicating that thepartition mode information is a 2N×2N type and the prediction modeinformation is not the intra prediction mode.

The luminance compensation determiner 14 may determine luminancecompensation information for the current block included in a slicedetermined to use luminance compensation based on the partition modeinformation and the prediction mode information.

The luminance compensation determiner 14 may omit an operation ofdetermining whether to perform luminance compensation on second layerblocks except for the block determined as the predetermined partitionmode and prediction mode.

The second layer encoder 16 may not perform residual prediction, on thesecond layer block determined to have luminance compensation performedthereon, that predicts residual information of the second layer blockusing residual information of at least one reference block of a timedirection reference block and an interlayer direction reference block.Thus, information indicating whether to perform residual prediction maybe determined with respect to only a block (a slice or a picture)determined not to have luminance compensation performed thereon?.

The second layer encoder 16 may not perform a luminance compensationoperation, between luminance of the first layer reference block andluminance of the second layer block, on the second layer blockdetermined to perform residual prediction that predicts the residualinformation of the second layer block by using the residual informationof at least one reference block of the time direction reference blockand the interlayer direction reference block.

The luminance of the second layer block may be determined throughcompensation of the luminance or without compensating for the luminanceaccording to determination of the luminance compensation determiner 14.Thus, in operation 17, the second layer encoder 16 may generate thesecond layer bitstream including the inter layer prediction informationbetween the second layer current block of which luminance is determinedaccording to whether to perform luminance compensation and the firstlayer reference block.

If the luminance of the second layer image is adjusted in considerationof the first layer image, since errors between the first layer image andthe second layer image are further reduced, encoding efficiency of interlayer prediction may be improved. Compensation of luminance may beprioritized in a specific encoding mode according to an encoding mode ofa block.

The interlayer video encoding apparatus 10 according to variousembodiments may include a central processor (not shown) that generallycontrols the first layer encoder 12, the luminance compensationdeterminer 14, and the second layer encoder 16. Alternatively, the firstlayer encoder 12, the luminance compensation determiner 14, and thesecond layer encoder 16 may operate by their respective processors (notshown), and the interlayer video encoding apparatus 10 may generallyoperate according to interactions of the processors (not shown).Alternatively, the first layer encoder 12, the luminance compensationdeterminer 14, and the second layer encoder 16 may be controlledaccording to the control of an external processor (not shown) of theinterlayer video encoding apparatus 10.

The interlayer video encoding apparatus 10 may include one or more datastorage units (not shown) in which input and output data of the firstlayer encoder 12, the luminance compensation determiner 14, and thesecond layer encoder 16 is stored. The interlayer video encodingapparatus 10 may include a memory control unit (not shown) that observesdata input and output of the data storage units (not shown).

The interlayer video encoding apparatus 10 may operate in connectionwith an internal video encoding processor or an external video encodingprocessor so as to output video encoding results, thereby performing avideo encoding operation including transformation. The internal videoencoding processor of the interlayer video encoding apparatus 10 may beimplemented by a central processor or a graphic processor as well as aseparate processor.

FIG. 2A is a block diagram of an interlayer video decoding apparatus 20,according to various embodiments.

The interlayer video decoding apparatus 20 according to variousembodiments may include a second layer encoder 22, a luminancecompensation determiner 24, and a second layer decoder 26. The luminancecompensation determiner 24 may be included in the second layer decoder26. The luminance compensation determiner 24 according to anotherembodiment may be located outside the second layer decoder 26.

The interlayer video decoding apparatus 20 according to variousembodiments may receive bitstreams for each layer according to scalableencoding. The number of layers of the bitstreams received by theinterlayer video decoding apparatus 20 is not limited. However, forconvenience of description, an embodiment in which the second layerencoder 22 of the interlayer video decoding apparatus 20 receives anddecodes a first layer stream and the second layer decoder 26 receivesand decodes a second layer stream will be described in detail.

For example, the interlayer video decoding apparatus 20 based on spatialscalability may receive streams in which image sequences of differentresolutions are encoded according to different layers. A low resolutionimage sequence may be reconstructed by decoding the first layer stream,and a high resolution image sequence may be reconstructed by decodingthe second layer stream.

As another example, a multi-view video may be decoded according toscalable video coding. When a stereoscopic video stream is received inmultiple layers, the first layer stream may be decoded to reconstructleft view images. The second layer stream may be further decoded to thefirst layer stream to reconstruct right view images.

Alternatively, when a multi-view video stream is received in multiplelayers, the first layer stream may be decoded to reconstruct center viewimages. The second layer stream may be further decoded to the firstlayer stream to reconstruct the left view images. A third layer streammay be further decoded to the first layer stream to reconstruct theright view images.

As another example, scalable video coding based on temporal scalabilitymay be performed. The first layer stream may be decoded to reconstructbase frame rate images. The second layer stream may be further decodedto the first layer stream to reconstruct high speed frame rate images.

In the presence of three or more second layers, first layer images maybe reconstructed from the first layer stream. If the second layer streamis further decoded by referring to the first layer reconstructionimages, second layer images may be further reconstructed. If a Kth layerstream is further decoded by referring to the second layerreconstruction images, Kth layer images may be further reconstructed.

The interlayer video decoding apparatus 20 may obtain encoded data ofthe first layer images and second layer images from the first layerstream and the second layer stream and may further obtain a motionvector generated through inter prediction and prediction informationgenerated through inter layer prediction.

For example, the interlayer video decoding apparatus 20 may decodeinter-predicted data for each layer and may decode inter layer-predicteddata between a plurality of layers. Reconstruction may be performedthrough motion compensation and inter layer decoding based on a codingunit or a prediction unit.

Motion compensation for a current image is performed by referring toreconstruction images predicted through inter prediction of a same layeron each layer stream, and thus images may be reconstructed. Motioncompensation means an operation of synthesizing a reference imagedetermined by using a motion vector of the current image and a residualof the current image and reconfiguring a reconstruction image of thecurrent image.

The interlayer video decoding apparatus 20 may perform inter-layerdecoding with reference to prediction information of the first layerimages so as to decode a second layer image predicted throughinter-layer prediction. Inter-layer decoding means an operation ofreconfiguring a reconstruction image of the current image bysynthesizing a reference image of a different layer determined topredict a current image and a residual of the current image.

The interlayer video decoding apparatus 20 according to an embodimentmay perform inter-layer decoding for reconstructing the third layerimages predicted with reference to the second layer images. Aninterlayer prediction structure will be described in detail withreference to FIG. 3 later.

However, the second layer encoder 26 according to various embodimentsmay decode the second layer stream without referring to the first layerimage sequence. Thus, it is not limited to construe that the secondlayer encoder 26 performs only inter-layer prediction in order to decodethe second layer image sequence.

The interlayer video decoding apparatus 20 decodes each image of a videofor each block. A block according to an exemplary embodiment may includea maximum encoding unit, an encoding unit, a prediction unit, atransformation unit, etc. among encoding units according to a treestructure.

The first layer encoder 22 may decode the first layer image by usingencoding symbols of a parsed first layer image. If the interlayer videodecoding apparatus 20 receives encoded streams based on coding unitshaving a tree structure, the first layer encoder 22 may perform decodingbased on the coding units having the tree structure for each maximumcoding unit of the first layer stream.

The first layer encoder 22 may perform entropy encoding for each maximumcoding unit and may obtain encoding information and encoded data. Thefirst layer encoder 22 may perform inverse quantization and inversetransformation on the encoded data obtained from streams to reconstructa residual. The first layer encoder 22 according to another embodimentmay directly receive a bitstream of quantized transformationcoefficients. A residual of the images may be reconstructed as a resultof performing inverse quantization and inverse transformation on thequantized transformation coefficients.

The first layer encoder 22 may reconstruct the first layer images bysynthesizing a prediction image and the residual through motioncompensation between same layer images.

The second layer encoder 26 may generate a second layer prediction imageby using samples of a first layer reconstruction image according to theinter layer prediction structure. The second layer encoder 26 may decodethe second layer stream to obtain a prediction error according to interlayer prediction. The second layer encoder 26 may combine the secondlayer prediction image and the prediction error, thereby generating thesecond layer reconstruction image.

The second layer encoder 26 may determine the second layer predictionimage using the first layer reconstruction image decoded by the firstlayer encoder 22. The second layer encoder 26 may determine a block ofthe first layer image to which a block such as a coding unit or aprediction unit of the second layer image is to refer according to theinter layer prediction structure. That is, a block of the first layerimage to which a block of the second layer image is to refer may bedetermined. For example, a reconstruction block of the first layer imagelocated in the second layer image in correspondence to a location of acurrent block may be determined. The second layer encoder 26 maydetermine a second layer prediction block using a first layerreconstruction block corresponding to a second layer block.

The second layer encoder 26 may use the second layer prediction blockdetermined using the first layer reconstruction block according to aninterlayer prediction structure as a reference image for interlayerpredicting a second layer original block. In this case, the second layerencoder 26 may reconstruct the second layer block by synthesizing asample value of the second layer prediction block determined using thefirst layer reconstruction image and a residual according to interlayerprediction.

According to spatial scalable video coding, when the first layer decoder22 reconstructs the first layer image of a different resolution fromthat of the second layer image, the second layer decoder 26 mayinterpolate the first layer reconstruction image to resize the firstlayer reconstruction image to have the same resolution as that of thesecond layer original image. The interpolated first layer reconstructionimage may be determined as the second layer prediction image forinterlayer prediction.

Therefore, the first layer decoder 22 of the interlayer video decodingapparatus 20 may reconstruct the first layer image sequence by decodingthe first layer stream, and the second layer decoder 26 may reconstructthe second layer image sequence by decoding the second layer stream.

In consideration of a luminance mismatch between views, the luminancecompensation determiner 24 of the interlayer video decoding apparatus 20may compensate for and reconstruct a luminance difference between videosfor each view. For example, a luminance difference between a first viewimage decoded by the first layer decoder 22 and a second view imagedecoded by the second layer decoder 26 may be acquired from a bitstream.Since the luminance difference between the second view image and thefirst view image is acquired, it may be determined whether to performluminance compensation when the second layer decoder 26 decodes a secondview video.

The luminance compensation determiner 24 according to variousembodiments may determine whether to perform luminance compensation inconsideration of characteristics of a predetermined data unit such as aslice of a current image or a block.

A detailed operation of the interlayer video decoding apparatus 20 thatconsiders compensation of luminance will now be described with referenceto FIG. 2B.

FIG. 2B is a flowchart of an interlayer video decoding method, accordingto various embodiments.

In operation 21, the first layer decoder 22 may reconstruct a firstlayer image based on encoding information acquired from a first layerbitstream.

In operation 23, the second layer decoder 26 may determine a secondlayer reconstruction block using a first layer reference blockcorresponding to a second layer block in a first layer reconstructionimage according to an interlayer prediction structure.

That is, the second layer decoder 26 may determine a partition mode anda prediction mode of a second layer current block by using the interlayer prediction information acquired from a second layer bitstream andusing the first layer reference block corresponding to a current blockthat is to be reconstructed from a second layer in the first layerreconstruction image.

In operation 25, the luminance compensation determiner 24 may determinewhether to perform luminance compensation on the second layer currentblock in a partition mode in which the second layer current block is notsplit. In this regard, the partition mode in which the second layercurrent block is not split may be a 2N×2N partition mode.

In operation 27, the second layer decoder 26 may perform luminancecompensation on the second layer current block according to whether toperform luminance compensation and reconstruct the second layer imageincluding the second layer current block on which luminance compensationis performed. The second layer decoder 26 may compensate for a luminancedifference between the first layer reference block and the second layerblock in order to reconstruct the second layer block that is determinedto perform luminance compensation thereon by the luminance compensationdeterminer 24. In this regard, information regarding the luminancedifference between layers may be acquired from a bitstream.Alternatively, the information regarding the luminance differencebetween layers may be induced by utilizing peripheral pixel values ofthe second layer current block and peripheral pixel values of the firstlayer reconstruction block corresponding to the current block.Alternatively, a luminance value of the second layer block may becompensated for by as much as a preset luminance.

According to an embodiment, luminance compensation may overlap withinter layer prediction. A reconstruction sample of the second layerblock may be determined by additionally compensating for luminance of asample of the second layer block determined by compensating for aresidual of a reconstruction sample of the first layer block accordingto the inter layer prediction structure.

According to another embodiment, luminance compensation may not beperformed simultaneously with inter layer prediction. Since a luminancedifference may be included in a residual between layers according to theinter layer prediction structure, the luminance of the sample of thesecond layer block determined by compensating for the residual of thereconstruction sample of the first layer block according to the interlayer prediction structure may not be compensated for. However,luminance of the second layer block in which the residual between layersis not compensated for may be compensated for.

Operation 25 will now be described in more detail.

The luminance compensation determiner 24 may acquire partition modeinformation and prediction mode information of a second layer block froma second layer bitstream. The luminance compensation determiner 24 mayacquire luminance compensation information for the second layer blockfrom the second layer bitstream when the partition mode information isthe partition mode in which the second layer current block is not splitand the prediction mode is not an intra prediction mode. For example,the prediction mode information of the second layer block may bedetermined by a merge mode or advanced motion vector prediction (AMVP)mode.

The luminance compensation determiner 24 may determine whether toperform luminance compensation on the second layer block, based on theluminance compensation information for the second layer block.

The luminance compensation determiner 24 may acquire luminancecompensation information for a block indicating that a size of thesecond layer block is 2N×2N and the partition mode information is a2N×2N partition mode.

The luminance compensation determiner 24 may acquire luminancecompensation information for a block indicating that the partition modeinformation is a 2N×2N type and the prediction mode information is notthe intra prediction mode.

As another example, the luminance compensation determiner 24 may acquireluminance compensation information for the current block included in aslice determined to use luminance compensation based on the partitionmode information and the prediction mode information.

The luminance compensation determiner 24 may omit an operation ofdetermining whether to perform luminance compensation on second layerblocks except for the block determined as the predetermined partitionmode and prediction mode.

The luminance compensation determiner 24 according to an embodiment mayacquire information indicating whether to perform residual prediction ononly a block (a slice or a picture) determined not to have luminancecompensation performed thereon. Thus, the luminance compensationdeterminer 24 may not perform residual prediction on the second layerblock determined to have luminance compensation performed thereon, thatpredicts residual information of the second layer block using residualinformation of at least one reference block of a time directionreference block and an interlayer direction reference block.

The luminance compensation determiner 24 according to another embodimentmay acquire information indicating whether to perform luminancecompensation on only a block (a slice or a picture) determined not tohave residual prediction performed thereon. Thus, the luminancecompensation determiner 24 may not perform luminance compensation on thesecond layer block determined to have performed thereon residualprediction that predicts the residual information of the second layerblock by using the residual information of at least one reference blockof the time direction reference block and the interlayer directionreference block, by compensating for a luminance difference of a samplevalue of the first layer reference block and determining a sample valueof the second layer block.

However, according to the interlayer encoding method, a partition modeor a prediction mode of the second layer block may be determined in thesame way as a partition mode and a prediction mode of the first layerblock corresponding to the second layer block. In this case, althoughthe luminance compensation determiner 24 is disposed outside the secondlayer decoder 26, the partition mode and the prediction mode of thesecond layer block may be predicted using sample values of the partitionmode information and the prediction mode information of the first layerblock. Thus, the luminance compensation determiner 24 may determinewhether to perform luminance compensation on the second layer blockbased on the predicted partition mode and prediction mode of the secondlayer block.

The interlayer video decoding apparatus 20 according to variousembodiments may include a central processor (not shown) that generallycontrols the first layer decoder 22, the luminance compensationdeterminer 24, and the second layer decoder 26. Alternatively, the firstlayer decoder 22, the luminance compensation determiner 24, and thesecond layer decoder 26 may operate by their respective processors (notshown), and the interlayer video decoding apparatus 20 may generallyoperate according to interactions of the processors (not shown).Alternatively, the first layer decoder 22, the luminance compensationdeterminer 24, and the second layer decoder 26 may be controlledaccording to the control of an external processor (not shown) of theinterlayer video decoding apparatus 20.

The interlayer video decoding apparatus 20 according to variousembodiments may include one or more data storage units (not shown) inwhich input and output data of the first layer decoder 22, the luminancecompensation determiner 24, and the second layer decoder 26 is stored.The interlayer video decoding apparatus 20 may include a memory controlunit (not shown) that observes data input and output of the data storageunits (not shown).

The interlayer video decoding apparatus 20 according to variousembodiments may operate in connection with an internal video decodingprocessor or an external video decoding processor so as to output videodecoding results, thereby performing a video decoding operationincluding transformation. The internal video decoding processor of theinterlayer video decoding apparatus 20 may be implemented by a centralprocessor or a graphic processor as well as a separate processor.

Referring to FIGS. 2A and 2B, the interlayer video decoding apparatus 20may compensate for a luminance difference between images or views ofdifferent layers with respect to a specific type of block or sliceduring a process of decoding the second layer image, and thus luminancebetween the first layer reconstruction image and the second layerreconstruction image may be uniform. Referring to FIGS. 1A and 1B, theinterlayer video encoding apparatus 10 may perform luminancecompensation between images of different layers with respect to aspecific type of block or slice, and thus a residual between aprediction image and an original image may be reduced.

A luminance compensation application range of a multilayer image isappropriately restricted, thereby maintaining encoding efficiency andreducing complexity.

FIG. 3 illustrates an inter-layer prediction structure, according to anembodiment.

The inter layer video encoding apparatus 10 according to an embodimentmay prediction encode base view images, left view images, and right viewimages according to a reproduction order 30 of a multi-view videoprediction structure shown in FIG. 3.

According to the reproduction order 30 of the multi-view videoprediction structure of the related art, images of the same view may bearranged in a horizontal direction. Thus, left view images “Left” may bearranged in a line in the horizontal direction, base view images“Center” may be arranged in a line in the horizontal direction, andright view images “Right” may be arranged in a line in the horizontaldirection. The base view images may be center view images compared tothe left and right view images.

Images having the same POC order may be arranged in a verticaldirection. A POC of images is a reproduction order of imagesconstituting video. “POC X” in the reproduction order 30 of themulti-view video prediction structure indicates a relative reproductionorder of images positioned in a corresponding column. The smaller thenumber of X, the earlier the reproduction order, and the greater thenumber of X, the later the reproduction order.

Therefore, according to the reproduction order 30 of the multi-viewvideo prediction structure of the related art, the left view images“Left” may be arranged in the horizontal direction according to the POC(reproduction order), the base view images “Center” may be in thehorizontal direction according to the POC (reproduction order), and theright view images “Right” may be arranged in the horizontal directionaccording to the POC (reproduction order). The left and right viewimages positioned in the same column as that of the base view imageshave different views but have the same POC (reproduction order).

Four consecutive images of view images constitute a single GOP. Each GOPincludes images between consecutive anchor pictures and a single keypicture.

An anchor picture is a random access point. In this regard, when apredetermined reproduction position is selected from images that arearranged according to a reproduction order of video, that is, accordingto a POC, an anchor picture of which a POC is closest to thereproduction position is reproduced. The base view images include baseview anchor pictures 31, 32, 33, 33, and 35, the left view imagesinclude left view anchor pictures 131, 132, 133, 134, and 135, and theright view images include right view anchor pictures 231, 232, 233, 234,and 235.

Multi-view images may be reproduced and predicted (restored) accordingto a GOP order. According to the reproduction order 30 of the multi-viewvideo prediction structure, images included in a GOP 0 are reproducedaccording to views and then images included in a GOP 1 may bereproduced. That is, images included in each GOP may be reproduced inthe order of GOP 0, GOP 1, GOP 2, and GOP 3. According to a coding orderof the multi-view video prediction structure, the images included in theGOP 0 are predicted (restored) according to views and then the imagesincluded in the GOP 1 may be predicted (restored). That is, the imagesincluded in each GOP may be reproduced in the order of GOP 0, GOP 1, GOP2, and GOP 3.

According to the reproduction order 30 of the multi-view videoprediction structure, both inter-view prediction (inter layerprediction) and inter prediction may be performed on images. In themulti-view video prediction structure, an image from which an arrowstarts, and an image to which an arrow is directed is an image that ispredicted by using the reference image.

A predicting result of the base view images may be encoded and then maybe output in the form of a base view image stream, and a predictionresult of the additional view images may be encoded and then may beoutput in the form of a layer bitstream. In addition, a predictingresult of the left view images may be output in a first layer bitstreamand a predicting result of the right view images may be output in asecond layer bitstream.

Only inter prediction is performed on base view images. That is, theanchor pictures 51, 52, 53, 54, and 55 that are I-picture type picturesdo not refer to different images, whereas the remaining images that areB-picture type images and b-picture type images are predicted withreference to different base view images. The B-picture type images arepredicted with reference to an I-picture type anchor picture having apreceding POC order and an I-picture type anchor picture having a laterPOC order. B-picture type images are predicted with reference to anI-picture type anchor picture having a preceding POC order and aB-picture type image having a later POC order or a B-picture type imagehaving a preceding POC order and an I-picture type anchor picture havinga later POC order.

Inter-view prediction (inter layer prediction) referring to differentview images and inter prediction referring to the same view images arerespectively performed on the left view images and the right viewimages.

Inter-view prediction (inter layer prediction) may be performed on theleft view anchor pictures 131, 132, 133, 134, and 135, respectively,with reference to the base view anchor pictures 31, 32, 33, 34, and 35having the same POC order. Inter-view prediction may be performed on theright view anchor pictures 231, 232, 233, 234, and 235, respectively,with reference to the base view anchor pictures 31, 32, 33, 34, and 35or the left view anchor pictures 131, 132, 133, 134, and 135 having thesame POC order. Inter-view prediction (inter layer prediction) referringto different view images having the same POC order may be performed onremaining merge images among the left view images and the right viewimages, other than the anchor pictures 131, 132, 133, 134, 135, 231,232, 233, 234, and 235.

The remaining merge images among the left view images and the right viewimages, other than the anchor pictures 131, 132, 133, 134, 135, 231,232, 233, 234, and 235 are predicted with reference to the same viewimages.

However, the left view images and the right view images may not bepredicted with reference to an anchor picture having a previousreproduction order among additional view images of the same view. Thatis, for inter prediction of a current left view image, the left viewimages except for a left view anchor picture having a reproduction orderprevious to that of the current left view image may be referred to.Likewise, for inter prediction of a current right view image, the rightview images except for a right view anchor picture having a reproductionorder previous to that of the current right view image may be referredto.

For inter prediction of the current left view image, prediction may beperformed by not referring to a left view image that belongs to a GOPprevious to a current GPO to which the current left view belongs but byreferring to a left view image that belongs to the current GOP and is tobe reconstructed before the current left view image. The right viewimage is the same as described above.

The inter layer video decoding apparatus 20 according to an embodimentmay prediction encode base view images, left view images, and right viewimages according to the reproduction order 30 of a multi-view videoprediction structure shown in FIG. 3.

The left view images may be reconstructed via inter-view disparitycompensation referring to the base view images and inter-view motioncompensation referring to the left view images. The right view imagesmay be reconstructed via inter-view disparity compensation referring tothe base view images and the left view images and inter-view motioncompensation referring to the right view images. Reference images needto be firstly reconstructed for disparity compensation and motioncompensation of the left view images and the right view images.

For inter-view motion compensation of the left view images, the leftview images may be reconstructed via inter-view motion compensationreferring to reconstructed left view reference images. For inter-viewmotion compensation of the right view images, the right view images maybe reconstructed via inter-view motion compensation referring toreconstructed right view reference images.

For inter-view motion compensation of the current left view image,prediction may be performed by not referring to a left view image thatbelongs to a GOP previous to a current GPO to which the current leftview belongs but by referring to a left view image that belongs to thecurrent GOP and is to be reconstructed before the current left viewimage. The right view image is the same as described above.

As described above, the interlayer video encoding apparatus 10 and theinterlayer video decoding apparatus 20 may determine whether to performluminance compensation according to image characteristics. Theinterlayer video encoding apparatus 10 and the interlayer video decodingapparatus 20 may determine whether to perform luminance compensation foreach slice or block.

The interlayer video encoding apparatus 10 and the interlayer videodecoding apparatus 20 may compensate for luminance of not only a lumablock but also a chroma block in the same way.

For example, a coding unit having a size of 2N×2N may be split intoprediction units having sizes 2N×2N, N×2N, 2N×N, or N×N. In this regard,partition mode information indicating shapes of the prediction units maybe determined as 2N×2N, N×2N, 2N×N, or N×N. In this regard, according toan embodiment, it may be determined whether to perform luminancecompensation on only a block having a partition mode of 2N×2N.

As another example, it may be determined whether to perform luminancecompensation on a current block based on encoding characteristics suchas a picture type of a picture to which a block belongs, a temporallevel, a network abstraction unit (NAL) type, and a distance between acurrent image and a reference image in temporal prediction. According tothe encoding characteristics, an encoding mode having a high possibilityof statistically needing luminance compensation may be preset. It may bedetermined whether to perform luminance compensation on a block of apreset encoding mode.

As another example, it may be determined whether to perform luminancecompensation according to an encoding mode determined for each block.For example, when a block is in a predetermined encoding mode in eachslice, luminance compensation information indicating whether to performluminance compensation may be transmitted or received as slice data or aslice header. Alternatively, when a block is in a predetermined encodingmode in each picture, luminance compensation information indicatingwhether to perform luminance compensation may be transmitted or receivedas a PPS or picture related data.

For example, it may be determined whether to perform luminancecompensation on a block determined according to rate-distortionoptimization based on a prediction direction and a coding unit of theblock.

A method of determining whether to perform luminance compensationaccording to various embodiments will now be described with reference toFIGS. 4 through 6 below.

An embodiment in which it is determined whether to perform luminancecompensation when a partition mode of a current block is 2N×2N will nowbe described with reference to FIG. 4 below. Embodiments of syntax forperforming luminance compensation based on a partition mode of a currentblock will now be described with reference to FIGS. 5 and 6 below.

FIG. 4 is a flowchart of a method in which the interlayer video decodingapparatus 20 performs luminance compensation, according to anembodiment.

In operation 41, the luminance compensation determiner 24 of theinterlayer video decoding apparatus 20 may acquire prediction modeinformation and partition mode information of a current block anddetermine whether a partition mode of the current block is a 2N×2Npartition mode. If the partition mode of the current block is not the2N×2N partition mode, the luminance compensation determiner 24 may end aprocess 40 without determining whether to perform luminancecompensation.

However, in operation 41, if the partition mode of the current block isthe 2N×2N partition mode, in operation 42, the luminance compensationdeterminer 24 may determine whether to perform luminance compensationand acquire ic_flag.

In operation 42, the luminance compensation determiner 24 may acquireluminance compensation information of the current block “ic_flag” anddetermine whether to perform luminance compensation from the luminancecompensation information “ic_flag”. The luminance compensationinformation of the current block “ic_flag” may be acquired from areceived stream or may be determined according to an encoding mode suchas a coding type or a prediction direction of the current block. Theluminance compensation determiner 24 may set “ic_flag” as 0 if notreceiving “ic_flag” from a bistream.

In operation 43, the luminance compensation determiner 24 may determinewhether the luminance compensation information “ic_flag” is 1, and, inoperation 44, may perform luminance compensation on a block on whichluminance compensation is to be performed.

Meanwhile, although an example in which the interlayer video decodingapparatus 20 determines whether to perform luminance compensation inoperations 41 through 44, it can be understood by one of ordinary skillin the art that the method described with reference to FIG. 4 may beperformed by the interlayer video encoding apparatus 10.

FIG. 5 illustrates an example of syntax for performing luminancecompensation based on a partition mode of a current block, according toan embodiment.

Syntax coding_unit( ) 50 for a current block may include conditionalsentences 56 and 57 for determining whether to perform luminancecompensation on the current block.

In the conditional sentence 56, when the current block is a skip mode(skip_flag[x0][y0]), if luminance compensation is possible on blocks ina slice (icEnableFlag==1), the luminance compensation information“ic_flag” may be used to indicate whether to perform luminancecompensation for the current block.

For example, “ic_flag” is set as 1 when luminance compensation on thecurrent block is used, and “ic_flag” is set as 0 or may not appear whenluminance compensation on the current block is not used.

FIG. 6 illustrates another example of syntax for performing luminancecompensation based on a partition mode of a current block, according toan embodiment.

Syntax cu_extension( ) 60 for a current block may include a conditionalsentence 61 for determining whether to perform luminance compensation onthe current block (ic_flag==1).

In the conditional sentence 61, if luminance compensation is possible onblocks in a slice (icEnableFlag==1), the luminance compensationinformation “ic_flag” may be used to indicate whether to performluminance compensation for the current block.

Therefore, when semantics of the syntax cu_extension( )60 may be definedto determine whether to perform luminance compensation((icEnableFlag==1?) on the current block when a partition mode of thecurrent block is 2N×2N. In more detail, the interlayer video decodingapparatus 20 may determine whether to perform luminance compensation((icEnableFlag==1?) when the partition mode of the current block is2N×2N, luminance compensation is set to be possible on a slice on whichthe current block belongs (slice_ic_enable_flag==1), and a predictionmode of the current block is not an intra mode (CuPredMode[x0][y0]!==MODE_INTRA).

In the conditional sentence 61, when luminance compensation is possible,“ic_flag” is set as 1 if luminance compensation on the current block isused, and “ic_flag” is set as 0 or may not appear if luminancecompensation on the current block is not used.

The interlayer video encoding apparatus 10 and the interlayer videodecoding apparatus 20 that determine whether to perform luminancecompensation on a block for each image characteristic have beendescribed with reference to FIGS. 1A through 6 above. If luminancecompensation is performed on all blocks, since operation load mayincrease, the interlayer video encoding apparatus 10 and the interlayervideo decoding apparatus 20 may determine whether to perform luminancecompensation on only a block satisfying a predetermined condition andmay not determine whether to perform luminance compensation on a blockthat does not satisfy the predetermined condition and may not performluminance compensation.

Therefore, it may be determined whether to perform luminancecompensation on a block encoded as a preset encoding mode. Luminancecompensation information indicating whether to perform luminancecompensation determined on the block of the encoding mode may beincluded in a transmission stream or may be acquired from a receivedstream.

Therefore, the interlayer video encoding apparatus 10 and the interlayervideo decoding apparatus 20 according to various embodiments maydetermine whether to perform luminance compensation only on a block thatfurther relatively needs luminance compensation and may not performluminance compensation on other blocks, thereby reducing operation loaddue to luminance compensation and improving encoding efficiency owing toluminance compensation.

In the interlayer video encoding apparatus 10 according to an embodimentand the interlayer video decoding apparatus 20 according to anembodiment, as described above, video data may be split into codingunits having a tree structure, and coding units, prediction units, andtransformation units are used for inter layer prediction or interprediction on the coding units. Hereinafter, a video encoding method andapparatus and a video decoding method and apparatus based on codingunits having a tree structure according to an embodiment will bedescribed with reference to FIGS. 7 through 19.

In principle, during encoding/decoding for multi-layer video,encoding/decoding processes for first layer images and encoding/decodingprocesses for second layer images are separately performed. That is,when inter-layer prediction is performed on a multi-layer video,encoding/decoding results of a single-layer video are referred to eachother, but separate encoding/decoding processes are performed forrespective single-layer videos.

For convenience of description, since a video encoding process and avideo decoding process based on a coding unit according to a treestructure, which will be described with reference to FIGS. 7 through 19,are performed on a single-layer video, only inter prediction and motioncompensation will be described. However, as described with reference toFIGS. 1A through 6, inter-layer prediction and compensation between baselayer images and second layer images are performed to encode/decode avideo stream.

Thus, when the first layer encoder 12 of the interlayer video encodingapparatus 10 according to an embodiment encodes a multi-layer videobased on a coding unit according to a tree structure, in order to encodea video for each respective single-view video, the interlayer videoencoding apparatus 10 includes as many video encoding apparatuses 100 ofFIG. 7 as the number of layers of the multi-layer video in order toencode a video such that each video encoding apparatus 100 may becontrolled to encode an assigned single-layer video. In addition, theinterlayer video encoding apparatus 10 may perform inter-view predictionby using the encoding results of separate single-views of each videoencoding apparatus 100. Thus, the first layer encoder 12 of theinterlayer video encoding apparatus 10 may generate a base layer videostream and a second layer video stream, in which the encoding resultsfor respective layers are recorded, for each respective hierarchy.

Similarly, when the second layer encoder 26 of the interlayer videodecoding apparatus 20 according to an embodiment decodes a multi-layervideo based on a coding unit according to a tree structure, in order todecode the received base layer video stream and second layer videostream for each respective layer, the interlayer video decodingapparatus 20 may include as many video decoding apparatuses 200 of FIG.8 as the number of layers of the multi-view video and the video decodingapparatuses 200 may be controlled to perform decoding on single-layervideos that are respectively assigned to the video decoding apparatuses200. In addition, the interlayer video encoding apparatus 10 may performinter-view compensation by using the decoding result of separatesingle-layer of each video decoding apparatuses 200. Thus, the secondlayer encoder 26 of the interlayer video decoding apparatus 20 maygenerate first layer images and second layer images, which are restoredfor respective layers.

FIG. 7 is a block diagram of the video encoding apparatus 100 based oncoding units according to a tree structure, according to one or moreembodiments.

The video encoding apparatus 100 involving video prediction based oncoding units according to a tree structure includes a LCU splitter 110,a coding unit determiner 120, and an outputter 130.

The LCU splitter 110 may split a current picture based on a LCU that isa coding unit having a maximum size for a current picture of an image.If the current picture is larger than the LCU, image data of the currentpicture may be split into the at least one LCU. The LCU according to oneor more embodiments may be a data unit having a size of 32×32, 64×64,128×128, 256×256, etc., wherein a shape of the data unit is a squarehaving a width and length in squares of 2. The image data may be outputto the coding unit determiner 120 according to the at least one LCU.

A coding unit according to one or more embodiments may be characterizedby a maximum size and a depth. The depth denotes the number of times thecoding unit is spatially split from the LCU, and as the depth deepens,deeper coding units according to depths may be split from the LCU to asmallest coding unit (SCU). A depth of the LCU is an uppermost depth anda depth of the SCU is a lowermost depth. Since a size of a coding unitcorresponding to each depth decreases as the depth of the LCU deepens, acoding unit corresponding to an upper depth may include a plurality ofcoding units corresponding to lower depths.

As described above, the image data of the current picture is split intothe LCUs according to a maximum size of the coding unit, and each of theLCUs may include deeper coding units that are split according to depths.Since the LCU according to one or more embodiments is split according todepths, the image data of the space domain included in the LCU may behierarchically classified according to depths.

A maximum depth and a maximum size of a coding unit, which limit thetotal number of times a height and a width of the LCU are hierarchicallysplit, may be predetermined.

The coding unit determiner 120 encodes at least one split regionobtained by splitting a region of the LCU according to depths, anddetermines a depth to output a finally encoded image data according tothe at least one split region. In other words, the coding unitdeterminer 120 determines a depth by encoding the image data in thedeeper coding units according to depths, according to the LCU of thecurrent picture, and selecting a depth having the least encoding error.The determined depth and the encoded image data according to thedetermined depth are output to the outputter 130.

The image data in the LCU is encoded based on the deeper coding unitscorresponding to at least one depth equal to or below the maximum depth,and results of encoding the image data are compared based on each of thedeeper coding units. A depth having the least encoding error may beselected after comparing encoding errors of the deeper coding units. Atleast one depth may be selected for each LCU.

The size of the LCU is split as a coding unit is hierarchically splitaccording to depths, and as the number of coding units increases. Also,even if coding units correspond to the same depth in one LCU, it isdetermined whether to split each of the coding units corresponding tothe same depth to a lower depth by measuring an encoding error of theimage data of the each coding unit, separately. Accordingly, even whenimage data is included in one LCU, the encoding errors may differaccording to regions in the one LCU, and thus the depths may differaccording to regions in the image data. Thus, one or more depths may bedetermined in one LCU, and the image data of the LCU may be dividedaccording to coding units of at least one depth.

Accordingly, the coding unit determiner 120 may determine coding unitshaving a tree structure included in the LCU. The ‘coding units having atree structure’ according to one or more embodiments include codingunits corresponding to a depth determined to be the depth, from amongall deeper coding units included in the LCU. A coding unit of a depthmay be hierarchically determined according to depths in the same regionof the LCU, and may be independently determined in different regions.Similarly, a depth in a current region may be independently determinedfrom a depth in another region.

A maximum depth according to one or more embodiments is an index relatedto the number of splitting times from a LCU to an SCU. A first maximumdepth according to one or more embodiments may denote the total numberof splitting times from the LCU to the SCU. A second maximum depthaccording to one or more embodiments may denote the total number ofdepth levels from the LCU to the SCU. For example, when a depth of theLCU is 0, a depth of a coding unit, in which the LCU is split once, maybe set to 1, and a depth of a coding unit, in which the LCU is splittwice, may be set to 2. Here, if the SCU is a coding unit in which theLCU is split four times, 5 depth levels of depths 0, 1, 2, 3, and 4exist, and thus the first maximum depth may be set to 4, and the secondmaximum depth may be set to 5.

Prediction encoding and transformation may be performed according to theLCU. The prediction encoding and the transformation are also performedbased on the deeper coding units according to a depth equal to or depthsless than the maximum depth, according to the LCU.

Since the number of deeper coding units increases whenever the LCU issplit according to depths, encoding, including the prediction encodingand the transformation, is performed on all of the deeper coding unitsgenerated as the depth deepens. For convenience of description, theprediction encoding and the transformation will now be described basedon a coding unit of a current depth, in a LCU.

The video encoding apparatus 100 may variously select a size or shape ofa data unit for encoding the image data. In order to encode the imagedata, operations, such as prediction encoding, transformation, andentropy encoding, are performed, and at this time, the same data unitmay be used for all operations or different data units may be used foreach operation.

For example, the video encoding apparatus 100 may select not only acoding unit for encoding the image data, but also a data unit differentfrom the coding unit so as to perform the prediction encoding on theimage data in the coding unit.

In order to perform prediction encoding in the LCU, the predictionencoding may be performed based on a coding unit corresponding to adepth, i.e., based on a coding unit that is no longer split to codingunits corresponding to a lower depth. Hereinafter, the coding unit thatis no longer split and becomes a basis unit for prediction encoding willnow be referred to as a ‘prediction unit’. A partition obtained bysplitting the prediction unit may include a prediction unit or a dataunit obtained by splitting at least one of a height and a width of theprediction unit. A partition is a data unit where a prediction unit of acoding unit is split, and a prediction unit may be a partition havingthe same size as a coding unit.

For example, when a coding unit of 2N×2N (where N is a positive integer)is no longer split and becomes a prediction unit of 2N×2N, and a size ofa partition may be 2N×2N, 2N×N, N×2N, or N×N. Examples of a partitionmode include symmetrical partitions that are obtained by symmetricallysplitting a height or width of the prediction unit, partitions obtainedby asymmetrically splitting the height or width of the prediction unit,such as 1:n or n:1, partitions that are obtained by geometricallysplitting the prediction unit, and partitions having arbitrary shapes.

A prediction mode of the prediction unit may be at least one of an intramode, a inter mode, and a skip mode. For example, the intra mode or theinter mode may be performed on the partition of 2N×2N, 2N×N, N×2N, orN×N. Also, the skip mode may be performed only on the partition of2N×2N. The encoding is independently performed on one prediction unit ina coding unit, thereby selecting a prediction mode having a leastencoding error.

The video encoding apparatus 100 may also perform the transformation onthe image data in a coding unit based not only on the coding unit forencoding the image data, but also based on a data unit that is differentfrom the coding unit. In order to perform the transformation in thecoding unit, the transformation may be performed based on a data unithaving a size smaller than or equal to the coding unit. For example, thedata unit for the transformation may include a data unit for an intramode and a data unit for an inter mode.

The transformation unit in the coding unit may be recursively split intosmaller sized regions in the similar manner as the coding unit accordingto the tree structure. Thus, residues in the coding unit may be dividedaccording to the transformation unit having the tree structure accordingto transformation depths.

A transformation depth indicating the number of splitting times to reachthe transformation unit by splitting the height and width of the codingunit may also be set in the transformation unit. For example, in acurrent coding unit of 2N×2N, a transformation depth may be 0 when thesize of a transformation unit is 2N×2N, may be 1 when the size of thetransformation unit is N×N, and may be 2 when the size of thetransformation unit is N/2×N/2. In other words, the transformation unithaving the tree structure may be set according to the transformationdepths.

Encoding information according to coding units corresponding to a depthrequires not only information about the depth, but also aboutinformation related to prediction encoding and transformation.Accordingly, the coding unit determiner 120 not only determines a depthhaving a least encoding error, but also determines a partition mode in aprediction unit, a prediction mode according to prediction units, and asize of a transformation unit for transformation.

Coding units according to a tree structure in a LCU and methods ofdetermining a prediction unit/partition, and a transformation unit,according to one or more embodiments, will be described in detail belowwith reference to FIGS. 8 through 19.

The coding unit determiner 120 may measure an encoding error of deepercoding units according to depths by using Rate-Distortion Optimizationbased on Lagrangian multipliers.

The outputter 130 outputs the image data of the LCU, which is encodedbased on the at least one depth determined by the coding unit determiner120, and information about the encoding mode according to the depth, inbitstreams.

The encoded image data may be obtained by encoding residues of an image.

The information about the encoding mode according to depth may includeinformation about the depth, about the partition mode in the predictionunit, the prediction mode, and the size of the transformation unit.

The information about the depth may be defined by using splittinginformation according to depths, which indicates whether encoding isperformed on coding units of a lower depth instead of a current depth.If the current depth of the current coding unit is the depth, image datain the current coding unit is encoded and output, and thus the splittinginformation may be defined not to split the current coding unit to alower depth. Alternatively, if the current depth of the current codingunit is not the depth, the encoding is performed on the coding unit ofthe lower depth, and thus the splitting information may be defined tosplit the current coding unit to obtain the coding units of the lowerdepth.

If the current depth is not the depth, encoding is performed on thecoding unit that is split into the coding unit of the lower depth. Sinceat least one coding unit of the lower depth exists in one coding unit ofthe current depth, the encoding is repeatedly performed on each codingunit of the lower depth, and thus the encoding may be recursivelyperformed for the coding units having the same depth.

Since the coding units having a tree structure are determined for oneLCU, and information about at least one encoding mode is determined fora coding unit of a depth, information about at least one encoding modemay be determined for one LCU. Also, a depth of the image data of theLCU may be different according to locations since the image data ishierarchically split according to depths, and thus splitting informationmay be set for the image data.

Accordingly, the outputter 130 may assign corresponding splittinginformation to at least one of the coding unit, the prediction unit, anda minimum unit included in the LCU.

The minimum unit according to one or more embodiments is a square dataunit obtained by splitting the SCU constituting the lowermost depth by4. Alternatively, the minimum unit according to an embodiment may be amaximum square data unit that may be included in all of the codingunits, prediction units, partition units, and transformation unitsincluded in the LCU.

For example, the encoding information output by the outputter 130 may beclassified into encoding information according to deeper coding units,and encoding information according to prediction units. The encodinginformation according to the deeper coding units may include theinformation about the prediction mode and about the size of thepartitions. The encoding information according to the prediction unitsmay include information about an estimated direction of an inter mode,about a reference image index of the inter mode, about a motion vector,about a chroma component of an intra mode, and about an interpolationmethod of the intra mode.

Information about a maximum size of the coding unit defined according topictures, slices, or GOPs, and information about a maximum depth may beinserted into a header of a bitstream, a sequence parameter set, or apicture parameter set.

Information about a maximum size of the transformation unit permittedwith respect to a current video, and information about a minimum size ofthe transformation unit may also be output through a header of abitstream, a sequence parameter set, or a picture parameter set. Theoutputter 130 may encode and output SAO parameters related to the SAOoperation described above with reference to FIGS. 1A through 14.

In the video encoding apparatus 100, the deeper coding unit may be acoding unit obtained by dividing a height or width of a coding unit ofan upper depth, which is one layer above, by two. In other words, whenthe size of the coding unit of the current depth is 2N×2N, the size ofthe coding unit of the lower depth is N×N. Also, the coding unit withthe current depth having a size of 2N×2N may include a maximum of 4 ofthe coding units with the lower depth.

Accordingly, the video encoding apparatus 100 may form the coding unitshaving the tree structure by determining coding units having an optimumshape and an optimum size for each LCU, based on the size of the LCU andthe maximum depth determined considering characteristics of the currentpicture. Also, since encoding may be performed on each LCU by using anyone of various prediction modes and transformations, an optimum encodingmode may be determined considering characteristics of the coding unit ofvarious image sizes.

Thus, if an image having a high resolution or a large data amount isencoded in a conventional macroblock, the number of macroblocks perpicture excessively increases. Accordingly, the number of pieces ofcompressed information generated for each macroblock increases, and thusit is difficult to transmit the compressed information and datacompression efficiency decreases. However, by using the video encodingapparatus 100, image compression efficiency may be increased since acoding unit is adjusted while considering characteristics of an imagewhile increasing a maximum size of a coding unit while considering asize of the image.

The interlayer video encoding apparatus 10 described with reference toFIG. 1A may include as many video encoding apparatuses 100 as the numberof layers in order to encode single-layer images for respective layersof a multi-layer video. For example, the first layer encoder 12 mayinclude a single video encoding apparatus 100 and the disparity vectordeterminer 14 may include as many video encoding apparatuses 100 as thenumber of additional views.

When the video encoding apparatus 100 encodes first layer images, thecoding determiner 120 may determine a prediction unit for interprediction for each respective coding unit according to a tree structurefor each largest coding unit and may perform inter prediction for eachrespective prediction unit.

When the video encoding apparatus 100 encodes second layer images, thecoding determiner 120 may also determine a prediction unit and a codingunit according to a tree structure for each largest coding unit and mayperform inter prediction for each respective prediction unit.

The video encoding apparatus 100 may encode a brightness differencebetween first and second layer images for compensating for thebrightness difference. However, whether to perform brightnesscompensation may be determined according to an encoding mode of a codingunit. For example, the brightness compensation may be performed only ona prediction unit of 2N×2N.

FIG. 8 is a block diagram of the video decoding apparatus 200 based oncoding units having a tree structure, according to one or moreembodiments.

The video decoding apparatus 200 that involves video prediction based oncoding units having a tree structure includes a receiver 210, an imagedata and encoding information extractor 220, and an image data decoder230.

Definitions of various terms, such as a coding unit, a depth, aprediction unit, a transformation unit, and information about variousencoding modes, for decoding operations of the video decoding apparatus200 are identical to those described with reference to FIG. 8 and thevideo encoding apparatus 100.

The receiver 210 receives and parses a bitstream of an encoded video.The image data and encoding information extractor 220 extracts encodedimage data for each coding unit from the parsed bitstream, wherein thecoding units have a tree structure according to each LCU, and outputsthe extracted image data to the image data decoder 230. The image dataand encoding information extractor 220 may extract information about amaximum size of a coding unit of a current picture, from a header aboutthe current picture, a sequence parameter set, or a picture parameterset.

Also, the image data and encoding information extractor 220 extractssplitting information and encoding information for the coding unitshaving a tree structure according to each LCU, from the parsedbitstream. The extracted splitting information and encoding informationare output to the image data decoder 230. In other words, the image datain a bit stream is split into the LCU so that the image data decoder 230decodes the image data for each LCU.

The splitting information and encoding information according to the LCUmay be set for at least one piece of splitting information correspondingto the depth, and encoding information according to the depth mayinclude information about a partition mode of a corresponding codingunit corresponding to the depth, information about a prediction mode,and splitting information of a transformation unit. Also, splittinginformation according to depths may be extracted as the informationabout a final depth.

The splitting information and the encoding information according to eachLCU extracted by the image data and encoding information extractor 220is splitting information and encoding information determined to generatea minimum encoding error when an encoder, such as the video encodingapparatus 100, repeatedly performs encoding for each deeper coding unitaccording to depths according to each LCU. Accordingly, the videodecoding apparatus 200 may reconstruct an image by decoding the imagedata according to a depth and an encoding mode that generates theminimum encoding error.

Since the splitting information and the encoding information may beassigned to a predetermined data unit from among a corresponding codingunit, a prediction unit, and a minimum unit, the image data and encodinginformation extractor 220 may extract the splitting information and theencoding information according to the predetermined data units. Ifsplitting information and encoding information of a corresponding LCUare recorded according to predetermined data units, the predetermineddata units to which the same splitting information and encodinginformation are assigned may be inferred to be the data units includedin the same LCU.

The image data decoder 230 reconstructs the current picture by decodingthe image data in each LCU based on the splitting information and theencoding information according to the LCUs. In other words, the imagedata decoder 230 may decode the encoded image data based on theextracted information about the partition mode, the prediction mode, andthe transformation unit for each coding unit from among the coding unitshaving the tree structure included in each LCU. A decoding process mayinclude a prediction including intra prediction and motion compensation,and an inverse transformation.

The image data decoder 230 may perform intra prediction or motioncompensation according to a partition and a prediction mode of eachcoding unit, based on the information about the partition mode and theprediction mode of the prediction unit of the coding unit according todepths.

In addition, the image data decoder 230 may read information about atransformation unit according to a tree structure for each coding unitso as to perform inverse transformation based on transformation unitsfor each coding unit, for inverse transformation for each LCU. Via theinverse transformation, a pixel value of the space domain of the codingunit may be reconstructed.

The image data decoder 230 may determine a final depth of a current LCUby using splitting information according to depths. If the splittinginformation indicates that image data is no longer split in the currentdepth, the current depth is the final depth. Accordingly, the image datadecoder 230 may decode encoded data in the current LCU by using theinformation about the partition mode of the prediction unit, theinformation about the prediction mode, and the splitting information ofthe transformation unit for each coding unit corresponding to the depth.

In other words, data units containing the encoding information includingthe same splitting information may be gathered by observing the encodinginformation set assigned for the predetermined data unit from among thecoding unit, the prediction unit, and the minimum unit, and the gathereddata units may be considered to be one data unit to be decoded by theimage data decoder 230 in the same encoding mode. As such, the currentcoding unit may be decoded by obtaining the information about theencoding mode for each coding unit.

The interlayer video decoding apparatus 20 described with reference toFIG. 2A may include as many video decoding apparatuses 200 as the numberof views in order to decode the received first layer image stream andsecond layer image stream to restore first layer images and second layerimages.

When a first layer image stream is received, the image data decoder 230of the video decoding apparatus 200 may split samples of first layerimages that are extracted from the first layer image stream by theextractor 220 into coding units according to a tree structure of alargest coding unit. The image data decoder 230 may perform motioncompensation on respective prediction units for inter prediction foreach respective coding unit according to a tree structure of the samplesof the first layer images, to restore the first layer images.

When a second layer image stream is received, the image data decoder 230of the video decoding apparatus 200 may split samples of second layerimages that are extracted from the second layer image stream by theextractor 220 into coding units according to a tree structure of alargest coding unit. The image data decoder 230 may perform motioncompensation on respective prediction units for inter prediction of thesamples of the second layer images to restore the second layer images.

The extractor 220 may obtain information relating to a brightness orderbetween first and second layer images from a bitstream in order tocompensate for the brightness difference. However, whether to performbrightness compensation may be determined according to an encoding modeof a coding unit. For example, the brightness compensation may beperformed only on a prediction unit of 2N×2N.

The video decoding apparatus 200 may obtain information about at leastone coding unit that generates the minimum encoding error when encodingis recursively performed for each largest coding unit, and may use theinformation to decode the current picture. In other words, the codingunits having the tree structure determined to be the optimum codingunits in each largest coding unit may be decoded. Also, the maximum sizeof a coding unit is determined considering a resolution and an amount ofimage data.

Accordingly, even if image data has high resolution and a large amountof data, the image data may be efficiently decoded and restored by usinga size of a coding unit and an encoding mode, which are adaptivelydetermined according to characteristics of the image data, by usinginformation about an optimum encoding mode received from an encoder.

FIG. 9 is a diagram for describing a concept of coding units accordingto various embodiments.

A size of a coding unit may be expressed by width×height, and may be64×64, 32×32, 16×16, and 8×8. A coding unit of 64×64 may be split intopartitions of 64×64, 64×32, 32×64, or 32×32, and a coding unit of 32×32may be split into partitions of 32×32, 32×16, 16×32, or 16×16, a codingunit of 16×16 may be split into partitions of 16×16, 16×8, 8×16, or 8×8,and a coding unit of 8×8 may be split into partitions of 8×8, 8×4, 4×8,or 4×4.

In video data 310, a resolution is 1920×1080, a maximum size of a codingunit is 64, and a maximum depth is 2. In video data 320, a resolution is1920×1080, a maximum size of a coding unit is 64, and a maximum depth is3. In video data 330, a resolution is 352×288, a maximum size of acoding unit is 16, and a maximum depth is 1. The maximum depth shown inFIG. 9 denotes a total number of splits from a LCU to a minimum decodingunit.

If a resolution is high or a data amount is large, a maximum size of acoding unit may be large so as to not only increase encoding efficiencybut also to accurately reflect characteristics of an image. Accordingly,the maximum size of the coding unit of the video data 310 and 320 havinga higher resolution than the video data 330 may be 64.

Since the maximum depth of the video data 310 is 2, coding units 315 ofthe vide data 310 may include a LCU having a long axis size of 64, andcoding units having long axis sizes of 32 and 16 since depths aredeepened to two layers by splitting the LCU twice. Since the maximumdepth of the video data 330 is 1, coding units 335 of the video data 330may include a LCU having a long axis size of 16, and coding units havinga long axis size of 8 since depths are deepened to one layer bysplitting the LCU once.

Since the maximum depth of the video data 320 is 3, coding units 325 ofthe video data 320 may include a LCU having a long axis size of 64, andcoding units having long axis sizes of 32, 16, and 8 since the depthsare deepened to 3 layers by splitting the LCU three times. As a depthdeepens, detailed information may be precisely expressed.

FIG. 10 is a block diagram of an image encoder 400 based on codingunits, according to one or more embodiments.

The image encoder 400 performs operations necessary for encoding imagedata in the coding unit determiner 120 of the video encoding apparatus100. In other words, an intra predictor 420 performs intra prediction oncoding units in an intra mode according to prediction units, from amonga current frame 405, and an inter predictor 415 performs interprediction on coding units in an inter mode by using a current image 405and a reference image obtained from a reconstructed picture buffer 410according to prediction units. The current image 405 may be split intoLCUs and then the LCUs may be sequentially encoded. In this regard, theLCUs that are to be split into coding units having a tree structure maybe encoded.

Residue data is generated by removing prediction data regarding codingunits of each mode that is output from the intra predictor 420 or theinter predictor 415 from data regarding encoded coding units of thecurrent image 405, and is output as a quantized transformationcoefficient according to transformation units through a transformer 425and a quantizer 430. The quantized transformation coefficient isreconstructed as the residue data in a space domain through adequantizer 445 and an inverse transformer 450. The reconstructedresidue data in the space domain is added to prediction data for codingunits of each mode that is output from the intra predictor 420 or theinter predictor and thus is reconstructed as data in a space domain forcoding units of the current image 405. The reconstructed data in thespace domain is generated as reconstructed images through a de-blocker455 and an SAO performer 460 and the reconstructed images are stored inthe reconstructed picture buffer 410. The reconstructed images stored inthe reconstructed picture buffer 410 may be used as reference images forinter prediction of another image. The transformation coefficientquantized by the transformer 425 and the quantizer 430 may be output asa bitstream 440 through an entropy encoder 435.

In order for the image encoder 400 to be applied in the video encodingapparatus 100, all elements of the image encoder 400, i.e., the interpredictor 415, the intra predictor 420, the transformer 425, thequantizer 430, the entropy encoder 435, the dequantizer 445, the inversetransformer 450, the de-blocker 455, and the SAO performer 460, performoperations based on each coding unit among coding units having a treestructure according to each LCU.

In particular, the intra predictor 410, the motion estimator 420, andthe motion compensator 425 determines partitions and a prediction modeof each coding unit from among the coding units having a tree structurewhile considering the maximum size and the maximum depth of a currentLCU, and the transformer 430 determines the size of the transformationunit in each coding unit from among the coding units having a treestructure.

Specifically, the intra predictor 420 and the inter predictor 415 maydetermine a partition mode and a prediction mode of each coding unitamong the coding units having a tree structure in consideration of amaximum size and a maximum depth of a current LCU, and the transformer425 may determine whether to split a transformation unit having a quadtree structure in each coding unit among the coding units having a treestructure.

FIG. 11 is a block diagram of an image decoder 500 based on codingunits, according to one or more embodiments.

An entropy decoder 515 parses encoded image data to be decoded andinformation about encoding required for decoding from a bitstream 505.The encoded image data is a quantized transformation coefficient fromwhich residue data is reconstructed by a dequantizer 520 and an inversetransformer 525.

An intra predictor 540 performs intra prediction on coding units in anintra mode according to each prediction unit. An inter predictor 535performs inter prediction on coding units in an inter mode from amongthe current image 405 for each prediction unit by using a referenceimage obtained from a reconstructed picture buffer 530.

Prediction data and residue data regarding coding units of each mode,which passed through the intra predictor 540 and the inter predictor535, are summed, and thus data in a space domain regarding coding unitsof the current image 405 may be reconstructed, and the reconstructeddata in the space domain may be output as a reconstructed image 560through a de-blocker 545 and an SAO performer 550. Reconstructed imagesstored in the reconstructed picture buffer 530 may be output asreference images.

In order to decode the image data in the image data decoder 230 of thevideo decoding apparatus 200, operations after the entropy decoder 515of the image decoder 500 according to an embodiment may be performed.

In order for the image decoder 500 to be applied in the video decodingapparatus 200 according to an embodiment, all elements of the imagedecoder 500, i.e., the entropy decoder 515, the dequantizer 520, theinverse transformer 525, the inter predictor 535, the de-blocker 545,and the SAO performer 550 may perform operations based on coding unitshaving a tree structure for each LCU.

In particular, the SAO performer 550 and the inter predictor 535 maydetermine a partition and a prediction mode for each of the coding unitshaving a tree structure, and the inverse transformer 525 may determinewhether to split a transformation unit having a quad tree structure foreach of the coding units.

The encoding operation of FIG. 10 and the encoding operation of FIG. 11describe video stream encoding and decoding operations in a singlelayer, respectively. Thus, if the first layer encoder 12 of FIG. 1Aencodes video streams of two or more layers, the image encoder 400 maybe provided for each layer. Similarly, if the second layer decoder 26 ofFIG. 2A decodes video streams of two or more layers, the image decoder500 may be provided for each layer

FIG. 12 is a diagram illustrating deeper coding units according todepths, and partitions, according to one or more embodiments.

The video encoding apparatus 100 and the video decoding apparatus 200use hierarchical coding units so as to consider characteristics of animage. A maximum height, a maximum width, and a maximum depth of codingunits may be adaptively determined according to the characteristics ofthe image, or may be differently set by a user. Sizes of deeper codingunits according to depths may be determined according to thepredetermined maximum size of the coding unit.

In a hierarchical structure 600 of coding units, according to one ormore embodiments, the maximum height and the maximum width of the codingunits are each 64, and the maximum depth is 3. In this case, the maximumdepth refers to a total number of times the coding unit is split fromthe LCU to the SCU. Since a depth deepens along a vertical axis of thehierarchical structure 600, a height and a width of the deeper codingunit are each split. Also, a prediction unit and partitions, which arebases for prediction encoding of each deeper coding unit, are shownalong a horizontal axis of the hierarchical structure 600.

In other words, a coding unit 610 is a LCU in the hierarchical structure600, wherein a depth is 0 and a size, i.e., a height by width, is 64×64.The depth deepens along the vertical axis, and a coding unit 620 havinga size of 32×32 and a depth of 1, a coding unit 630 having a size of16×16 and a depth of 2, and a coding unit 640 having a size of 8×8 and adepth of 3. The coding unit 640 having a size of 8×8 and a depth of 3 isan SCU.

The prediction unit and the partitions of a coding unit are arrangedalong the horizontal axis according to each depth. In other words, ifthe coding unit 610 having a size of 64×64 and a depth of 0 is aprediction unit, the prediction unit may be split into partitionsinclude in the encoding unit 610, i.e. a partition 610 having a size of64×64, partitions 612 having the size of 64×32, partitions 614 havingthe size of 32×64, or partitions 616 having the size of 32×32.

Similarly, a prediction unit of the coding unit 620 having the size of32×32 and the depth of 1 may be split into partitions included in thecoding unit 620, i.e. a partition 620 having a size of 32×32, partitions622 having a size of 32×16, partitions 624 having a size of 16×32, andpartitions 626 having a size of 16×16.

Similarly, a prediction unit of the coding unit 630 having the size of16×16 and the depth of 2 may be split into partitions included in thecoding unit 630, i.e. a partition having a size of 16×16 included in thecoding unit 630, partitions 632 having a size of 16×8, partitions 634having a size of 8×16, and partitions 636 having a size of 8×8.

Similarly, a prediction unit of the coding unit 640 having the size of8×8 and the depth of 3 may be split into partitions included in thecoding unit 640, i.e. a partition having a size of 8×8 included in thecoding unit 640, partitions 642 having a size of 8×4, partitions 644having a size of 4×8, and partitions 646 having a size of 4×4.

In order to determine a final depth of the coding units constituting theLCU 610, the coding unit determiner 120 of the video encoding apparatus100 performs encoding for coding units corresponding to each depthincluded in the LCU 610.

A number of deeper coding units according to depths including data inthe same range and the same size increases as the depth deepens. Forexample, four coding units corresponding to a depth of 2 are required tocover data that is included in one coding unit corresponding to a depthof 1. Accordingly, in order to compare encoding results of the same dataaccording to depths, the coding unit corresponding to the depth of 1 andfour coding units corresponding to the depth of 2 are each encoded.

In order to perform encoding for a current depth from among the depths,a least encoding error may be selected for the current depth byperforming encoding for each prediction unit in the coding unitscorresponding to the current depth, along the horizontal axis of thehierarchical structure 600. Alternatively, the minimum encoding errormay be searched for by comparing the least encoding errors according todepths, by performing encoding for each depth as the depth deepens alongthe vertical axis of the hierarchical structure 600. A depth and apartition having the minimum encoding error in the coding unit 610 maybe selected as the final depth and a partition mode of the coding unit610.

FIG. 13 is a diagram for describing a relationship between a coding unit710 and transformation units 720, according to one or more embodiments.

The video encoding apparatus 100 or the video decoding apparatus 200encodes or decodes an image according to coding units having sizessmaller than or equal to a LCU for each LCU. Sizes of transformationunits for transformation during encoding may be selected based on dataunits that are not larger than a corresponding coding unit.

For example, in the video encoding apparatus 100 or the video decodingapparatus 200, if a size of the coding unit 710 is 64×64, transformationmay be performed by using the transformation units 720 having a size of32×32.

Also, data of the coding unit 710 having the size of 64×64 may beencoded by performing the transformation on each of the transformationunits having the size of 32×32, 16×16, 8×8, and 4×4, which are smallerthan 64×64, and then a transformation unit having the least coding errormay be selected.

FIG. 14 is a diagram fro describing encoding information of coding unitscorresponding to a depth, according to one or more embodiments.

The outputter 130 of the video encoding apparatus 100 may encode andtransmit information 800 about a partition mode, information 810 about aprediction mode, and information 820 about a size of a transformationunit for each coding unit corresponding to a final depth, as informationabout an encoding mode.

The information 800 indicates information about a mode of a partitionobtained by splitting a prediction unit of a current coding unit,wherein the partition is a data unit for prediction encoding the currentcoding unit. For example, a current coding unit CU_0 having a size of2N×2N may be split into any one of a partition 802 having a size of2N×2N, a partition 804 having a size of 2N×N, a partition 806 having asize of N×2N, and a partition 808 having a size of N×N. Here, theinformation 800 about the partition mode is set to indicate one of thepartition 804 having a size of 2N×N, the partition 806 having a size ofN×2N, and the partition 808 having a size of N×N.

The information 810 indicates a prediction mode of each partition. Forexample, the information 810 may indicate a mode of prediction encodingperformed on a partition indicated by the information 800, i.e., anintra mode 812, an inter mode 814, or a skip mode 816.

The information 820 indicates a transformation unit to be based on whentransformation is performed on a current coding unit. For example, thetransformation unit may be a first intra transformation unit 822, asecond intra transformation unit 824, a first inter transformation unit826, or a second inter transformation unit 828.

The image data and encoding information extractor 220 of the videodecoding apparatus 200 may extract and use the information 800, 810, and820 for decoding, according to each deeper coding unit.

FIG. 15 is a diagram of deeper coding units according to depths,according to one or more embodiments.

Splitting information may be used to indicate a change of a depth. Thespilt information indicates whether a coding unit of a current depth issplit into coding units of a lower depth.

A prediction unit 910 for prediction encoding a coding unit 900 having adepth of 0 and a size of 2N_0×2N_0 may include partitions of a partitionmode 912 having a size of 2N_0×2N_0, a partition mode 914 having a sizeof 2N_0×N_0, a partition mode 916 having a size of N_0×2N_0, and apartition mode 918 having a size of N_0×N_0. FIG. 23 only illustratesthe partition modes 912 through 918 which are obtained by symmetricallysplitting the prediction unit 910, but a partition mode is not limitedthereto, and the partitions of the prediction unit 910 may includeasymmetrical partitions, partitions having a predetermined shape, andpartitions having a geometrical shape.

Prediction encoding is repeatedly performed on one partition having asize of 2N_0×2N_0, two partitions having a size of 2N_0×N_0, twopartitions having a size of N_0×2N_0, and four partitions having a sizeof N_0×N_0, according to each partition mode. The prediction encoding inan intra mode and an inter mode may be performed on the partitionshaving the sizes of 2N_0×2N_0, N_0×2N_0, 2N_0×N_0, and N_0×N_0. Theprediction encoding in a skip mode is performed only on the partitionhaving the size of 2N_0×2N_0.

If an encoding error is smallest in one of the partition modes 912through 916, the prediction unit 910 may not be split into a lowerdepth.

If the encoding error is the smallest in the partition mode 918, a depthis changed from 0 to 1 to split the partition mode 918 in operation 920,and encoding is repeatedly performed on coding units 930 having a depthof 2 and a size of N_0×N_0 to search for a minimum encoding error.

A prediction unit 940 for prediction encoding the coding unit 930 havinga depth of 1 and a size of 2N_1×2N_1 (=N_0×N_0) may include partitionsof a partition mode 942 having a size of 2N_1×2N_1, a partition mode 944having a size of 2N_1×N_1, a partition mode 946 having a size ofN_1×2N_1, and a partition mode 948 having a size of N_1×N_1.

If an encoding error is the smallest in the partition mode 948, a depthis changed from 1 to 2 to split the partition mode 948 in operation 950,and encoding is repeatedly performed on coding units 960, which have adepth of 2 and a size of N_2×N_2 to search for a minimum encoding error.

When a maximum depth is d, split operation according to each depth maybe performed up to when a depth becomes d-1, and splitting informationmay be encoded as up to when a depth is one of 0 to d-2. In other words,when encoding is performed up to when the depth is d-1 after a codingunit corresponding to a depth of d-2 is split in operation 970, aprediction unit 990 for prediction encoding a coding unit 980 having adepth of d-1 and a size of 2N_(d-1)×2N_(d-1) may include partitions of apartition mode 992 having a size of 2N_(d-1)×2N_(d-1), a partition mode994 having a size of 2N_(d-1)×N_(d-1), a partition mode 996 having asize of N_(d-1)×2N_(d-1), and a partition mode 998 having a size ofN_(d-1)×N_(d-1).

Prediction encoding may be repeatedly performed on one partition havinga size of 2N_(d-1)×2N_(d-1), two partitions having a size of2N_(d-1)×N_(d-1), two partitions having a size of N_(d-1)×2N_(d-1), fourpartitions having a size of N_(d-1)×N_(d-1) from among the partitionmodes 992 through 998 to search for a partition mode having a minimumencoding error.

Even when the partition mode 998 has the minimum encoding error, since amaximum depth is d, a coding unit CU_(d-1) having a depth of d-1 is nolonger split to a lower depth, and a depth for the coding unitsconstituting a current LCU 900 is determined to be d-1 and a partitionmode of the current LCU 900 may be determined to be N_(d-1)×N_(d-1).Also, since the maximum depth is d and an SCU 980 having a lowermostdepth of d-1 is no longer split to a lower depth, splitting informationfor the SCU 980 is not set.

A data unit 999 may be a ‘minimum unit’ for the current LCU. A minimumunit according to one or more embodiments may be a square data unitobtained by splitting an SCU 980 by 4. By performing the encodingrepeatedly, the video encoding apparatus 100 may select a depth havingthe least encoding error by comparing encoding errors according todepths of the coding unit 900 to determine a depth, and set acorresponding partition mode and a prediction mode as an encoding modeof the depth.

As such, the minimum encoding errors according to depths are compared inall of the depths of 1 through d, and a depth having the least encodingerror may be determined as a depth. The depth, the partition mode of theprediction unit, and the prediction mode may be encoded and transmittedas information about an encoding mode. Also, since a coding unit issplit from a depth of 0 to a depth, only splitting information of thedepth is set to 0, and splitting information of depths excluding thedepth is set to 1.

The image data and encoding information extractor 220 of the videodecoding apparatus 200 may extract and use the information about thedepth and the prediction unit of the coding unit 900 to decode thepartition 912. The video decoding apparatus 200 may determine a depth,in which splitting information is 0, as a depth by using splittinginformation according to depths, and use information about an encodingmode of the corresponding depth for decoding.

FIGS. 16 through 18 are diagrams for describing a relationship betweencoding units 1010, prediction units 1060, and transformation units 1070,according to one or more embodiments.

The coding units 1010 are coding units having a tree structure,corresponding to depths determined by the video encoding apparatus 100,in a LCU. The prediction units 1060 are partitions of prediction unitsof each of the coding units 1010, and the transformation units 1070 aretransformation units of each of the coding units 1010.

When a depth of a LCU is 0 in the coding units 1010, depths of codingunits 1012 and 1054 are 1, depths of coding units 1014, 1016, 1018,1028, 1050, and 1052 are 2, depths of coding units 1020, 1022, 1024,1026, 1030, 1032, and 1048 are 3, and depths of coding units 1040, 1042,1044, and 1046 are 4.

In the prediction units 1060, some encoding units 1014, 1016, 1022,1032, 1048, 1050, 1052, and 1054 are obtained by splitting the codingunits in the encoding units 1010. In other words, partition modes in thecoding units 1014, 1022, 1050, and 1054 have a size of 2N×N, partitionmodes in the coding units 1016, 1048, and 1052 have a size of N×2N, anda partition mode of the coding unit 1032 has a size of N×N. Predictionunits and partitions of the coding units 1010 are smaller than or equalto each coding unit.

Transformation or inverse transformation is performed on image data ofthe coding unit 1052 in the transformation units 1070 in a data unitthat is smaller than the coding unit 1052. Also, the coding units 1014,1016, 1022, 1032, 1048, 1050, and 1052 in the transformation units 1070are different from those in the prediction units 1060 in terms of sizesand shapes. In other words, the video encoding and decoding apparatuses100 and 200 may perform intra prediction, motion estimation, motioncompensation, transformation, and inverse transformation individually ona data unit in the same coding unit.

Accordingly, encoding is recursively performed on each of coding unitshaving a hierarchical structure in each region of a LCU to determine anoptimum coding unit, and thus coding units having a recursive treestructure may be obtained. Encoding information may include splittinginformation about a coding unit, information about a partition mode,information about a prediction mode, and information about a size of atransformation unit. Table 1 shows the encoding information that may beset by the video encoding and decoding apparatuses 100 and 200.

TABLE 1 Splitting information 0 (Encoding on Coding Unit having Size of2N × 2N and Current Depth of d) Size of Transformation Unit SplittingSplitting Partition mode information 0 information 1 SymmetricalAsymmetrical of of Prediction Partition Partition TransformationTransformation Splitting Mode mode mode Unit Unit information 1 Intra 2N× 2N 2N × nU 2N × 2N N × N Repeatedly Inter 2N × N 2N × nD (SymmetricalEncode Skip  N × 2N nL × 2N Type) Coding (Only  N × N nR × 2N N/2 × N/2Units 2N × 2N) (Asymmetrical having Type) Lower Depth of d + 1

The outputter 130 of the video encoding apparatus 100 may output theencoding information about the coding units having a tree structure, andthe image data and encoding information extractor 220 of the videodecoding apparatus 200 may extract the encoding information about thecoding units having a tree structure from a received bitstream.

Splitting information indicates whether a current coding unit is splitinto coding units of a lower depth. If splitting information of acurrent depth d is 0, a depth, in which a current coding unit is nolonger split into a lower depth, is a final depth, and thus informationabout a partition mode, prediction mode, and a size of a transformationunit may be defined for the final depth. If the current coding unit isfurther split according to the splitting information, encoding isindependently performed on four split coding units of a lower depth.

A prediction mode may be one of an intra mode, an inter mode, and a skipmode. The intra mode and the inter mode may be defined in all partitionmodes, and the skip mode is defined only in a partition mode having asize of 2N×2N.

The information about the partition mode may indicate symmetricalpartition modes having sizes of 2N×2N, 2N×N, N×2N, and N×N, which areobtained by symmetrically splitting a height or a width of a predictionunit, and asymmetrical partition modes having sizes of 2N×nU, 2N×nD,nL×2N, and nR×2N, which are obtained by asymmetrically splitting theheight or width of the prediction unit. The asymmetrical partition modeshaving the sizes of 2N×nU and 2N×nD may be respectively obtained bysplitting the height of the prediction unit in 1:3 and 3:1, and theasymmetrical partition modes having the sizes of nL×2N and nR×2N may berespectively obtained by splitting the width of the prediction unit in1:3 and 3:1

The size of the transformation unit may be set to be two types in theintra mode and two types in the inter mode. In other words, if splittinginformation of the transformation unit is 0, the size of thetransformation unit may be 2N×2N, which is the size of the currentcoding unit. If splitting information of the transformation unit is 1,the transformation units may be obtained by splitting the current codingunit. Also, if a partition mode of the current coding unit having thesize of 2N×2N is a symmetrical partition mode, a size of atransformation unit may be N×N, and if the partition mode of the currentcoding unit is an asymmetrical partition mode, the size of thetransformation unit may be N/2×N/2.

The encoding information about coding units having a tree structure mayinclude at least one of a coding unit corresponding to a depth, aprediction unit, and a minimum unit. The coding unit corresponding tothe depth may include at least one of a prediction unit and a minimumunit containing the same encoding information.

Accordingly, it is determined whether adjacent data units are includedin the same coding unit corresponding to the depth by comparing encodinginformation of the adjacent data units. Also, a corresponding codingunit corresponding to a depth is determined by using encodinginformation of a data unit, and thus a distribution of depths in a LCUmay be determined.

Accordingly, if a current coding unit is predicted based on encodinginformation of adjacent data units, encoding information of data unitsin deeper coding units adjacent to the current coding unit may bedirectly referred to and used.

Alternatively, if a current coding unit is predicted based on encodinginformation of adjacent data units, data units adjacent to the currentcoding unit are searched using encoded information of the data units,and the searched adjacent coding units may be referred for predictingthe current coding unit.

FIG. 19 is a diagram for describing a relationship between a codingunit, a prediction unit, and a transformation unit, according toencoding mode information of Table 1.

A LCU 1300 includes coding units 1302, 1304, 1306, 1312, 1314, 1316, and1318 of depths. Here, since the coding unit 1318 is a coding unit of adepth, splitting information may be set to 0. Information about apartition mode of the coding unit 1318 having a size of 2N×2N may be setto be one of a partition mode 1322 having a size of 2N×2N, a partitionmode 1324 having a size of 2N×N, a partition mode 1326 having a size ofN×2N, a partition mode 1328 having a size of N×N, a partition mode 1332having a size of 2N×nU, a partition mode 1334 having a size of 2N×nD, apartition mode 1336 having a size of nL×2N, and a partition mode 1338having a size of nR×2N.

Splitting information (TU size flag) of a transformation unit is a typeof a transformation index. The size of the transformation unitcorresponding to the transformation index may be changed according to aprediction unit type or partition mode of the coding unit.

For example, when the partition mode is set to be symmetrical, i.e. thepartition mode 1322, 1324, 1326, or 1328, a transformation unit 1342having a size of 2N×2N is set if a TU size flag of a transformation unitis 0, and a transformation unit 1344 having a size of N×N is set if a TUsize flag is 1.

When the partition mode is set to be asymmetrical, i.e., the partitionmode 1332, 1334, 1336, or 1338, a transformation unit 1352 having a sizeof 2N×2N is set if a TU size flag is 0, and a transformation unit 1354having a size of N/2×N/2 is set if a TU size flag is 1.

Referring to FIG. 19, the TU size flag is a flag having a value or 0 or1, but the TU size flag is not limited to 1 bit, and a transformationunit may be hierarchically split having a tree structure while the TUsize flag increases from 0. Splitting information (TU size flag) of atransformation unit may be an example of a transformation index.

In this case, the size of a transformation unit that has been actuallyused may be expressed by using a TU size flag of a transformation unit,according to one or more embodiments, together with a maximum size andminimum size of the transformation unit. The video encoding apparatus100 is capable of encoding maximum transformation unit size information,minimum transformation unit size information, and a maximum TU sizeflag. The result of encoding the maximum transformation unit sizeinformation, the minimum transformation unit size information, and themaximum TU size flag may be inserted into an SPS. The video decodingapparatus 200 may decode video by using the maximum transformation unitsize information, the minimum transformation unit size information, andthe maximum TU size flag.

For example, (a) if the size of a current coding unit is 64×64 and amaximum transformation unit size is 32×32, (a-1) then the size of atransformation unit may be 32×32 when a TU size flag is 0, (a-2) may be16×16 when the TU size flag is 1, and (a-3) may be 8×8 when the TU sizeflag is 2.

As another example, (b) if the size of the current coding unit is 32×32and a minimum transformation unit size is 32×32, (b-1) then the size ofthe transformation unit may be 32×32 when the TU size flag is 0. Here,the TU size flag cannot be set to a value other than 0, since the sizeof the transformation unit cannot be less than 32×32.

As another example, (c) if the size of the current coding unit is 64×64and a maximum TU size flag is 1, then the TU size flag may be 0 or 1.Here, the TU size flag cannot be set to a value other than 0 or 1.

Thus, if it is defined that the maximum TU size flag is‘MaxTransformSizeIndex’, a minimum transformation unit size is‘MinTransformSize’, and a transformation unit size is ‘RootTuSize’ whenthe TU size flag is 0, then a current minimum transformation unit size‘CurrMinTuSize’ that can be determined in a current coding unit, may bedefined by Equation (1):CurrMinTuSize=max(MinTransformSize,RootTuSize/(2^MaxTransformSizeIndex))  (1)

Compared to the current minimum transformation unit size ‘CurrMinTuSize’that can be determined in the current coding unit, a transformation unitsize ‘RootTuSize’ when the TU size flag is 0 may denote a maximumtransformation unit size that can be selected in the system. In Equation(1), ‘RootTuSize/(2^MaxTransformSizelndex)’ denotes a transformationunit size when the transformation unit size ‘RootTuSize’, when the TUsize flag is 0, is split a number of times corresponding to the maximumTU size flag, and ‘MinTransformSize’ denotes a minimum transformationsize. Thus, a smaller value from among‘RootTuSize/(2^MaxTransformSizelndex)’ and ‘MinTransformSize’ may be thecurrent minimum transformation unit size ‘CurrMinTuSize’ that can bedetermined in the current coding unit.

According to one or more embodiments, the maximum transformation unitsize RootTuSize may vary according to the type of a prediction mode.

For example, if a current prediction mode is an inter mode, then‘RootTuSize’ may be determined by using Equation (2) below. In Equation(2), ‘MaxTransformSize’ denotes a maximum transformation unit size, and‘PUSize’ denotes a current prediction unit size.RootTuSize=min(MaxTransformSize, PUSize)  (2)

That is, if the current prediction mode is the inter mode, thetransformation unit size ‘RootTuSize’, when the TU size flag is 0, maybe a smaller value from among the maximum transformation unit size andthe current prediction unit size.

If a prediction mode of a current partition unit is an intra mode,‘RootTuSize’ may be determined by using Equation (3) below. In Equation(3), ‘PartitionSize’ denotes the size of the current partition unit.RootTuSize=min(MaxTransformSize, PartitionSize)  (3)

That is, if the current prediction mode is the intra mode, thetransformation unit size ‘RootTuSize’ when the TU size flag is 0 may bea smaller value from among the maximum transformation unit size and thesize of the current partition unit.

However, the current maximum transformation unit size ‘RootTuSize’ thatvaries according to the type of a prediction mode in a partition unit isjust an example and the embodiments are not limited thereto.

According to the video encoding method based on coding units having atree structure as described with reference to FIGS. 7 through 19, imagedata of the space domain is encoded for each coding unit of a treestructure. According to the video decoding method based on coding unitshaving a tree structure, decoding is performed for each LCU toreconstruct image data of the space domain. Thus, a picture and a videothat is a picture sequence may be reconstructed. The reconstructed videomay be reproduced by a reproducing apparatus, stored in a storagemedium, or transmitted through a network.

The embodiments may be written as computer programs and may beimplemented in general-use digital computers that execute the programsusing a computer-readable recording medium. Examples of thecomputer-readable recording medium include magnetic storage media (e.g.,ROM, floppy discs, hard discs, etc.) and optical recording media (e.g.,CD-ROMs, or DVDs).

For convenience of description, the inter layer video encoding methodand/or the video encoding method described above with reference to FIGS.1A through 19, will be referred to as a ‘video encoding method accordingto the various embodiments’. In addition, the inter layer video decodingmethod and/or the video decoding method described above with referenceto FIGS. 1A through 19, will be referred to as a ‘video decoding methodaccording to the various embodiments’.

A video encoding apparatus including the inter layer video encodingapparatus 10, the video encoding apparatus 100, or the image encoder400, which is described above with reference to FIGS. 1A through 19,will be referred to as a ‘video encoding apparatus according to thevarious embodiments’. In addition, a video decoding apparatus includingthe inter layer video decoding apparatus 20, the video decodingapparatus 200, or the image decoder 500, which is described above withreference to FIGS. 1A through 19, will be referred to as a ‘videodecoding apparatus according to the various embodiments’.

A computer-readable recording medium storing a program, e.g., a disc26000, according to various embodiments will now be described in detail.

FIG. 20 is a diagram of a physical structure of the disc 26000 in whicha program is stored, according to one or more embodiments. The disc26000, which is a storage medium, may be a hard drive, a compactdisc-read only memory (CD-ROM) disc, a Blu-ray disc, or a digitalversatile disc (DVD). The disc 26000 includes a plurality of concentrictracks Tr that are each divided into a specific number of sectors Se ina circumferential direction of the disc 26000. In a specific region ofthe disc 26000, a program that executes the quantization parameterdetermination method, the video encoding method, and the video decodingmethod described above may be assigned and stored.

A computer system embodied using a storage medium that stores a programfor executing the video encoding method and the video decoding method asdescribed above will now be described with reference to FIG. 22.

FIG. 21 is a diagram of a disc drive 26800 for recording and reading aprogram by using the disc 26000. A computer system 26700 may store aprogram that executes at least one of a video encoding method and avideo decoding method according to one or more embodiments, in the disc26000 via the disc drive 26800. To run the program stored in the disc26000 in the computer system 26700, the program may be read from thedisc 26000 and be transmitted to the computer system 26700 by using thedisc drive 26700.

The program that executes at least one of a video encoding method and avideo decoding method according to one or more embodiments may be storednot only in the disc 26000 illustrated in FIG. 20 or 21 but also in amemory card, a ROM cassette, or a solid state drive (SSD).

A system to which the video encoding method and a video decoding methoddescribed above are applied will be described below.

FIG. 22 is a diagram of an overall structure of a content supply system11000 for providing a content distribution service. A service area of acommunication system is divided into predetermined-sized cells, andwireless base stations 11700, 11800, 11900, and 12000 are installed inthese cells, respectively.

The content supply system 11000 includes a plurality of independentdevices. For example, the plurality of independent devices, such as acomputer 12100, a personal digital assistant (PDA) 12200, a video camera12300, and a mobile phone 12500, are connected to the Internet 11100 viaan internet service provider 11200, a communication network 11400, andthe wireless base stations 11700, 11800, 11900, and 12000.

However, the content supply system 11000 is not limited to asillustrated in FIG. 22, and devices may be selectively connectedthereto. The plurality of independent devices may be directly connectedto the communication network 11400, not via the wireless base stations11700, 11800, 11900, and 12000.

The video camera 12300 is an imaging device, e.g., a digital videocamera, which is capable of capturing video images. The mobile phone12500 may employ at least one communication method from among variousprotocols, e.g., Personal Digital Communications (PDC), Code DivisionMultiple Access (CDMA), Wideband-Code Division Multiple Access (W-CDMA),Global System for Mobile Communications (GSM), and Personal HandyphoneSystem (PHS).

The video camera 12300 may be connected to a streaming server 11300 viathe wireless base station 11900 and the communication network 11400. Thestreaming server 11300 allows content received from a user via the videocamera 12300 to be streamed via a real-time broadcast. The contentreceived from the video camera 12300 may be encoded using the videocamera 12300 or the streaming server 11300. Video data captured by thevideo camera 12300 may be transmitted to the streaming server 11300 viathe computer 12100.

Video data captured by a camera 12600 may also be transmitted to thestreaming server 11300 via the computer 12100. The camera 12600 is animaging device capable of capturing both still images and video images,similar to a digital camera. The video data captured by the camera 12600may be encoded using the camera 12600 or the computer 12100. Softwarethat performs encoding and decoding video may be stored in acomputer-readable recording medium, e.g., a CD-ROM disc, a floppy disc,a hard disc drive, an SSD, or a memory card, which may be accessible bythe computer 12100.

If video data is captured by a camera built in the mobile phone 12500,the video data may be received from the mobile phone 12500.

The video data may also be encoded by a large scale integrated circuit(LSI) system installed in the video camera 12300, the mobile phone12500, or the camera 12600.

The content supply system 11000 may encode content data recorded by auser using the video camera 12300, the camera 12600, the mobile phone12500, or another imaging device, e.g., content recorded during aconcert, and transmit the encoded content data to the streaming server11300. The streaming server 11300 may transmit the encoded content datain a type of a streaming content to other clients that request thecontent data.

The clients are devices capable of decoding the encoded content data,e.g., the computer 12100, the PDA 12200, the video camera 12300, or themobile phone 12500. Thus, the content supply system 11000 allows theclients to receive and reproduce the encoded content data. Also, thecontent supply system 11000 allows the clients to receive the encodedcontent data and decode and reproduce the encoded content data in realtime, thereby enabling personal broadcasting.

Encoding and decoding operations of the plurality of independent devicesincluded in the content supply system 11000 may be similar to those of avideo encoding apparatus and a video decoding apparatus according to oneor more embodiments.

The mobile phone 12500 included in the content supply system 11000according to one or more embodiments will now be described in greaterdetail with referring to FIGS. 23 and 24.

FIG. 23 illustrates an external structure of the mobile phone 12500 towhich a video encoding method and a video decoding method are applied,according to one or more embodiments. The mobile phone 12500 may be asmart phone, the functions of which are not limited and a large numberof the functions of which may be changed or expanded.

The mobile phone 12500 includes an internal antenna 12510 via which aradio-frequency (RF) signal may be exchanged with the wireless basestation 12000 of FIG. 21, and includes a display screen 12520 fordisplaying images captured by a camera 12530 or images that are receivedvia the antenna 12510 and decoded, e.g., a liquid crystal display (LCD)or an organic light-emitting diode (OLED) screen. The mobile phone 12500includes an operation panel 12540 including a control button and a touchpanel. If the display screen 12520 is a touch screen, the operationpanel 12540 further includes a touch sensing panel of the display screen12520. The mobile phone 12500 includes a speaker 12580 for outputtingvoice and sound or another type of sound outputter, and a microphone12550 for inputting voice and sound or another type sound inputter. Themobile phone 12500 further includes the camera 12530, such as acharge-coupled device (CCD) camera, to capture video and still images.The mobile phone 12500 may further include a storage medium 12570 forstoring encoded/decoded data, e.g., video or still images captured bythe camera 12530, received via email, or obtained according to variousways; and a slot 12560 via which the storage medium 12570 is loaded intothe mobile phone 12500. The storage medium 12570 may be a flash memory,e.g., a secure digital (SD) card or an electrically erasable andprogrammable read only memory (EEPROM) included in a plastic case.

FIG. 24 illustrates an internal structure of the mobile phone 12500,according to one or more embodiments. To systemically control parts ofthe mobile phone 12500 including the display screen 12520 and theoperation panel 12540, a power supply circuit 12700, an operation inputcontroller 12640, an image encoder 12720, a camera interface 12630, anLCD controller 12620, an image decoder 12690, amultiplexer/demultiplexer 12680, a recorder/reader 12670, amodulator/demodulator 12660, and a sound processor 12650 are connectedto a central controller 12710 via a synchronization bus 12730.

If a user operates a power button and sets from a ‘power off’ state to a‘power on’ state, the power supply circuit 12700 supplies power to allthe parts of the mobile phone 12500 from a battery pack, thereby settingthe mobile phone 12500 in an operation mode.

The central controller 12710 includes a central processing unit (CPU), aROM, and a RAM.

While the mobile phone 12500 transmits communication data to theoutside, a digital signal is generated by the mobile phone 12500 undercontrol of the central controller 12710. For example, the soundprocessor 12650 may generate a digital sound signal, the image encoder12720 may generate a digital image signal, and text data of a messagemay be generated via the operation panel 12540 and the operation inputcontroller 12640. When a digital signal is transmitted to themodulator/demodulator 12660 under control of the central controller12710, the modulator/demodulator 12660 modulates a frequency band of thedigital signal, and a communication circuit 12610 performsdigital-to-analog conversion (DAC) and frequency conversion on thefrequency band-modulated digital sound signal. A transmission signaloutput from the communication circuit 12610 may be transmitted to avoice communication base station or the wireless base station 12000 viathe antenna 12510.

For example, when the mobile phone 12500 is in a conversation mode, asound signal obtained via the microphone 12550 is transformed into adigital sound signal by the sound processor 12650, under control of thecentral controller 12710. The digital sound signal may be transformedinto a transformation signal via the modulator/demodulator 12660 and thecommunication circuit 12610, and may be transmitted via the antenna12510.

When a text message, e.g., email, is transmitted in a data communicationmode, text data of the text message is input via the operation panel12540 and is transmitted to the central controller 12710 via theoperation input controller 12640. Under control of the centralcontroller 12710, the text data is transformed into a transmissionsignal via the modulator/demodulator 12660 and the communication circuit12610 and is transmitted to the wireless base station 12000 via theantenna 12510.

To transmit image data in the data communication mode, image datacaptured by the camera 12530 is provided to the image encoder 12720 viathe camera interface 12630. The captured image data may be directlydisplayed on the display screen 12520 via the camera interface 12630 andthe LCD controller 12620.

A structure of the image encoder 12720 may correspond to that of theabove-described video encoding method according to the one or moreembodiments. The image encoder 12720 may transform the image datareceived from the camera 12530 into compressed and encoded image databased on the above-described video encoding method according to the oneor more embodiments, and then output the encoded image data to themultiplexer/demultiplexer 12680. During a recording operation of thecamera 12530, a sound signal obtained by the microphone 12550 of themobile phone 12500 may be transformed into digital sound data via thesound processor 12650, and the digital sound data may be transmitted tothe multiplexer/demultiplexer 12680.

The multiplexer/demultiplexer 12680 multiplexes the encoded image datareceived from the image encoder 12720, together with the sound datareceived from the sound processor 12650. A result of multiplexing thedata may be transformed into a transmission signal via themodulator/demodulator 12660 and the communication circuit 12610, and maythen be transmitted via the antenna 12510.

While the mobile phone 12500 receives communication data from theoutside, frequency recovery and ADC are performed on a signal receivedvia the antenna 12510 to transform the signal into a digital signal. Themodulator/demodulator 12660 modulates a frequency band of the digitalsignal. The frequency-band modulated digital signal is transmitted tothe video decoding unit 12690, the sound processor 12650, or the LCDcontroller 12620, according to the type of the digital signal.

In the conversation mode, the mobile phone 12500 amplifies a signalreceived via the antenna 12510, and obtains a digital sound signal byperforming frequency conversion and ADC on the amplified signal. Areceived digital sound signal is transformed into an analog sound signalvia the modulator/demodulator 12660 and the sound processor 12650, andthe analog sound signal is output via the speaker 12580, under controlof the central controller 12710.

When in the data communication mode, data of a video file accessed at anInternet website is received, a signal received from the wireless basestation 12000 via the antenna 12510 is output as multiplexed data viathe modulator/demodulator 12660, and the multiplexed data is transmittedto the multiplexer/demultiplexer 12680.

To decode the multiplexed data received via the antenna 12510, themultiplexer/demultiplexer 12680 demultiplexes the multiplexed data intoan encoded video data stream and an encoded audio data stream. Via thesynchronization bus 12730, the encoded video data stream and the encodedaudio data stream are provided to the video decoding unit 12690 and thesound processor 12650, respectively.

A structure of the image decoder 12690 may correspond to that of theabove-described video decoding method according to the one or moreembodiments. The image decoder 12690 may decode the encoded video datato obtain reconstructed video data and provide the reconstructed videodata to the display screen 12520 via the LCD controller 12620, by usingthe above-described video decoding method according to the one or moreembodiments.

Thus, the data of the video file accessed at the Internet website may bedisplayed on the display screen 12520. At the same time, the soundprocessor 12650 may transform audio data into an analog sound signal,and provide the analog sound signal to the speaker 12580. Thus, audiodata contained in the video file accessed at the Internet website mayalso be reproduced via the speaker 12580.

The mobile phone 12500 or another type of communication terminal may bea transceiving terminal including both a video encoding apparatus and avideo decoding apparatus according to one or more embodiments, may be atransceiving terminal including only the video encoding apparatus, ormay be a transceiving terminal including only the video decodingapparatus.

A communication system according to the one or more embodiments is notlimited to the communication system described above with reference toFIG. 24. For example, FIG. 25 illustrates a digital broadcasting systememploying a communication system, according to one or more embodiments.The digital broadcasting system of FIG. 25 may receive a digitalbroadcast transmitted via a satellite or a terrestrial network by usinga video encoding apparatus and a video decoding apparatus according toone or more embodiments.

Specifically, a broadcasting station 12890 transmits a video data streamto a communication satellite or a broadcasting satellite 12900 by usingradio waves. The broadcasting satellite 12900 transmits a broadcastsignal, and the broadcast signal is transmitted to a satellite broadcastreceiver via a household antenna 12860. In every house, an encoded videostream may be decoded and reproduced by a TV receiver 12810, a set-topbox 12870, or another device.

When a video decoding apparatus according to one or more embodiments isimplemented in a reproducing apparatus 12830, the reproducing apparatus12830 may parse and decode an encoded video stream recorded on a storagemedium 12820, such as a disc or a memory card to reconstruct digitalsignals. Thus, the reconstructed video signal may be reproduced, forexample, on a monitor 12840.

In the set-top box 12870 connected to the antenna 12860 for asatellite/terrestrial broadcast or a cable antenna 12850 for receiving acable television (TV) broadcast, a video decoding apparatus according toone or more embodiments may be installed. Data output from the set-topbox 12870 may also be reproduced on a TV monitor 12880.

As another example, a video decoding apparatus according to one or moreembodiments may be installed in the TV receiver 12810 instead of theset-top box 12870.

An automobile 12920 that has an appropriate antenna 12910 may receive asignal transmitted from the satellite 12900 or the wireless base station11700. A decoded video may be reproduced on a display screen of anautomobile navigation system 12930 installed in the automobile 12920.

A video signal may be encoded by a video encoding apparatus according toone or more embodiments and may then be stored in a storage medium.Specifically, an image signal may be stored in a DVD disc 12960 by a DVDrecorder or may be stored in a hard disc by a hard disc recorder 12950.As another example, the video signal may be stored in an SD card 12970.If the hard disc recorder 12950 includes a video decoding apparatusaccording to one or more embodiments, a video signal recorded on the DVDdisc 12960, the SD card 12970, or another storage medium may bereproduced on the TV monitor 12880.

The automobile navigation system 12930 may not include the camera 12530of FIG. 26, and the camera interface 12630 and the image encoder 12720of FIG. 26. For example, the computer 12100 and the TV receiver 12810may not include the camera 12530, the camera interface 12630, and theimage encoder 12720.

FIG. 26 is a diagram illustrating a network structure of a cloudcomputing system using a video encoding apparatus and a video decodingapparatus, according to one or more embodiments.

The cloud computing system may include a cloud computing server 14000, auser database (DB) 14100, a plurality of computing resources 14200, anda user terminal.

The cloud computing system provides an on-demand outsourcing service ofthe plurality of computing resources 14200 via a data communicationnetwork, e.g., the Internet, in response to a request from the userterminal. Under a cloud computing environment, a service providerprovides users with desired services by combining computing resources atdata centers located at physically different locations by usingvirtualization technology. A service user does not have to installcomputing resources, e.g., an application, a storage, an operatingsystem (OS), and security, into his/her own terminal in order to usethem, but may select and use desired services from among services in avirtual space generated through the virtualization technology, at adesired point in time.

A user terminal of a specified service user is connected to the cloudcomputing server 14000 via a data communication network including theInternet and a mobile telecommunication network. User terminals may beprovided cloud computing services, and particularly video reproductionservices, from the cloud computing server 14000. The user terminals maybe various types of electronic devices capable of being connected to theInternet, e.g., a desktop PC 14300, a smart TV 14400, a smart phone14500, a notebook computer 14600, a portable multimedia player (PMP)14700, a tablet PC 14800, and the like.

The cloud computing server 14000 may combine the plurality of computingresources 14200 distributed in a cloud network and provide userterminals with a result of combining. The plurality of computingresources 14200 may include various data services, and may include datauploaded from user terminals. As described above, the cloud computingserver 14000 may provide user terminals with desired services bycombining video database distributed in different regions according tothe virtualization technology.

User information about users who have subscribed for a cloud computingservice is stored in the user DB 14100. The user information may includelogging information, addresses, names, and personal credit informationof the users. The user information may further include indexes ofvideos. Here, the indexes may include a list of videos that have alreadybeen reproduced, a list of videos that are being reproduced, a pausingpoint of a video that was being reproduced, and the like.

Information about a video stored in the user DB 14100 may be sharedbetween user devices. For example, when a video service is provided tothe notebook computer 14600 in response to a request from the notebookcomputer 14600, a reproduction history of the video service is stored inthe user DB 14100. When a request to reproduce this video service isreceived from the smart phone 14500, the cloud computing server 14000searches for and reproduces this video service, based on the user DB14100. When the smart phone 14500 receives a video data stream from thecloud computing server 14000, a process of reproducing video by decodingthe video data stream is similar to an operation of the mobile phone12500 described above with reference to FIG. 24.

The cloud computing server 14000 may refer to a reproduction history ofa desired video service, stored in the user DB 14100. For example, thecloud computing server 14000 receives a request to reproduce a videostored in the user DB 14100, from a user terminal. If this video wasbeing reproduced, then a method of streaming this video, performed bythe cloud computing server 14000, may vary according to the request fromthe user terminal, i.e., according to whether the video will bereproduced, starting from a start thereof or a pausing point thereof.For example, if the user terminal requests to reproduce the video,starting from the start thereof, the cloud computing server 14000transmits streaming data of the video starting from a first framethereof to the user terminal. If the user terminal requests to reproducethe video, starting from the pausing point thereof, the cloud computingserver 14000 transmits streaming data of the video starting from a framecorresponding to the pausing point, to the user terminal.

In this case, the user terminal may include a video decoding apparatusas described above with reference to FIGS. 1A through 19. As anotherexample, the user terminal may include a video encoding apparatus asdescribed above with reference to FIGS. 1A through 19. Alternatively,the user terminal may include both the video decoding apparatus and thevideo encoding apparatus as described above with reference to FIGS. 1Athrough 19.

Various applications of a video encoding method, a video decodingmethod, a video encoding apparatus, and a video decoding apparatusaccording to the one or more embodiments described above with referenceto FIGS. 1A through 19 have been described above with reference to FIGS.20 to 26. However, methods of storing the video encoding method and thevideo decoding method in a storage medium or methods of implementing thevideo encoding apparatus and the video decoding apparatus in a device,according to various embodiments, described above with reference toFIGS. 1A through 19 are not limited to the embodiments described abovewith reference to FIGS. 20 to 26.

It should be understood that the exemplary embodiments described thereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

While one or more embodiments of the present invention have beendescribed with reference to the figures, it will be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope of thepresent invention as defined by the following claims.

What is claimed is:
 1. An interlayer video decoding method comprising:reconstructing a first layer image based on encoding informationacquired from a first layer bitstream; reconstructing a second layercurrent block by using interlayer prediction information acquired from asecond layer bitstream and a first layer reference block correspondingto a current block of a first layer reconstruction image that is to bereconstructed in a second layer, wherein the second layer current blockis determined based on partition mode information and prediction modeinformation acquired from the second layer bitstream; acquiring, fromthe second layer bitstream, residual prediction information indicatingwhether to perform residual prediction on the second layer current blockwhen the partition mode information indicates a 2N×2N partition mode andthe prediction mode information indicates a prediction mode which is notan intra prediction mode; when the residual prediction informationindicates not to perform the residual prediction on the second layercurrent block, acquiring, from the second layer bitstream, luminancecompensation information indicating whether to perform luminancecompensation on the second layer current block, and compensating forluminance of the second layer current block based on the luminancecompensation information and reconstructing the second layer currentblock of which luminance is compensated for; and when the residualprediction information indicates to perform the residual prediction onthe second layer current block, not acquiring, from the second layerbitstream, the luminance compensation information, and performing theresidual prediction to reconstruct the second layer current block. 2.The interlayer video decoding method of claim 1, wherein the step ofacquiring luminance compensation information is omitted on second layerblocks except for blocks in the 2N×2N partition mode, and luminancecompensation is not performed on the second layer blocks.
 3. Theinterlayer video decoding method of claim 1, wherein the prediction modeis a merge mode or an advanced motion vector prediction (AMVP) mode. 4.An interlayer video decoding apparatus comprising: a first layer decoderfor reconstructing a first layer image based on encoding informationacquired from a first layer bitstream; and a second layer decoder forreconstructing a second layer current block by using interlayerprediction information acquired from a second layer bitstream and usinga first layer reference block corresponding to a current block of afirst layer reconstruction image that is to be reconstructed in a secondlayer, wherein the second layer current block is determined based onpartition mode information and prediction mode information acquired fromthe second layer bitstream, wherein: the second layer decoder acquires,from the second layer bitstream, residual prediction informationindicating whether to perform residual prediction on the second layercurrent block when the partition mode information indicates a 2N×2Npartition mode and the prediction mode information indicates aprediction mode which is not an intra prediction mode, when the residualprediction information indicates not to perform the residual predictionon the second layer current block, the second layer decoder acquires,from the second layer bitstream, luminance compensation informationindicating whether to perform luminance compensation on the second layercurrent block, and the second layer decoder compensates for luminance ofthe second layer current block based on the luminance compensationinformation and reconstructs the second layer current block of whichluminance is compensated for, and when the residual predictioninformation indicates to perform the residual prediction on the secondlayer current block, the second layer decoder does not acquires, fromthe second layer bitstream, the luminance cormpensation information, andthe second layer decoder performs the residual prediction to reconstructthe second layer current block.